CGM Diaries: Things I Wish I Knew

I last wrote about the Dexcom Continuous Glucose Monitor (CGM) on 11 December, 2017. In that post, I highlighted what it was like after a week. The first week was not without hiccups, and the following few weren't perfect either. Things have improved dramatically after almost two months of wearing a CGM. The idea behind this post is to share things I've learnt that weren't obvious from the beginning. These are the things that had I known in December, would've made the first few weeks with the CGM a lot smoother. Your mileage may vary, but this is a collection of what has been working for me.


Get your overnight blood sugar level right. That is the single best piece of advice I can give. The biggest annoyance I had with the CGM after a week was the alarms - especially overnight. There's no such thing as perfect control, and things are going to go wrong, but if you can stabilise the night as much as possible, it'll make your life easier. If you've got a CGM, chances are you're controlling your blood sugar levels through an insulin pump. It's important to fine-tune your basal insulin to a rate that will keep you steady overnight. Easier said than done, of course, but if it works 5 or 6 nights per week, you'll be well on your way to having an easier time with the CGM. Being woken three nights a week is no fun for anyone.

But how? Before getting a CGM, I would've told you that it was impossible to have consistent levels overnight. I've since learnt this isn't true. I noticed a correlation between the nights I had stabilised my blood sugar level before sleep (i.e. Was hovering at a constant level, and had no active insulin - this was key). Short-acting insulin stays in your system for just over three hours, so it's important to avoid eating carbs up to three hours before sleeping. I've changed habits to have dinner finished by 7 pm at the latest so that insulin is out of my system by 10 pm. Now I know that if by 10 pm my blood sugar is between 5 & 7 mmol/L, it's unlikely to fluctuate, thanks to no active insulin, and a good basal rate. The result? Hours of uninterrupted sleep. For the sake of your sanity, especially when it comes to alarms that can't be turned off, you'll want to ensure this stability. You may need to tweak basal insulin rates, but it's well worth the effort.

A stable night is advantageous for two reasons; it gets the day off to a good start and helps your average BGL for that day. If my average is higher than usual towards the end of the day, there's a good chance that a bad night was a contributing factor. Ultimately, the goal of using a CGM is to have better stability and control of your blood glucose, which shows in HbA1c results. If the first 6-8 hours of your day are spent at a healthy blood glucose level, that will go a long way to improving your HbA1c.

Bolus early, bolus often

The second most important piece of advice I can give is to bolus (or inject, if needles are your thing) well in advance of eating a meal. Something you'll likely notice during the early days with a CGM is the delay between giving insulin and when it takes effect. If you give insulin for food at the time you begin to eat, you'll see that the food takes effect well before the insulin does, resulting in a spike in your BGL, followed by a dip 60-120 minutes later as the bulk of the insulin takes effect. I've found that giving insulin 20-30 minutes before a meal is the best way to avoid this spike. Your mileage may vary, but I haven't had to worry about my blood sugar falling too fast when bolusing up to half an hour before a meal. Any earlier would put you at risk of a hypo before the food takes effect, so I don't recommend it. Avoiding this spike will not only make you feel better but will help stabilise your blood sugar after eating. The idea is that you then consume food around the time the insulin starts to act in your system, and they balance each other out. It's never perfect, but it may be the difference between "spiking" to 9 mmol/L rather than 13 mmol/L. Avoiding these higher blood sugar levels a few times a day will undoubtedly benefit your HbA1c result.

It's easy to bolus early when you know what you're going to eat at a prepared meal such as an at-home dinner. Eating lunch at uncertain times at work, or eating out and not knowing what to expect can make this quite difficult. You can't bolus 30 minutes in advance of a meal when you don't know what time you'll get around to eating, nor can you bolus correctly for a meal you've never seen before - as is the case when you eat at a restaurant. Years of diabetes management has taught me to guess the carbohydrate content of meals at a glance. Apply this skill to a plate of food you haven't seen before, and you might be able to guesstimate carb quantity in advance. For example, it's a safe bet that a plate of pasta will have a non-zero amount of carb, whereas fish and veggies will have very little carb. In the case of the former, I'd be looking to bolus early for approximately 50% of the carbs I expect in the pasta. A typical bowl might have 50g worth of carb, but as you don't know the portion size, nor when the meal will arrive, I don't recommend bolusing for the full 50g in advance. It's unlikely a bowl of pasta will have <25g, data-preserve-html-node="true" so start by bolusing for that in advance. When the meal arrives, you can use your amazing carb-guessing skills to deliver insulin for the rest of the meal. This has been working for me. Again, it might be different for you. Don't bolus early if your BGL is low to begin with, or if your BGL tends to drop right after bolusing. In my case, I know that if I give insulin for 25g carb, I can afford to wait 30 minutes before eating and still avoid a hypo. It's not always practical to bolus in advance, and that's okay. It isn't the end of the world - after all, it's what you've been doing for years, isn't it? If you're not confident guessing the carb content of a meal in advance or bolusing in advance of eating, you can either choose low-carb food to avoid a spike or just enjoy the meal and accept that a spike now and then is a part of having diabetes. Just be sure to check in with your BGL a few hours later and correct if need be.


The next thing I wish I knew is that carbs are bad. Actually, carbs are great. But carbs are bad for your blood glucose levels. You might've read the section above on sleeping and thought, "That's great, but it isn't possible for me to avoid eating within three hours of sleeping." That's fine! Just be more careful with what you choose to eat. You'll quickly realise the types of foods in your diet that need to go. Have a low (or no) carb dinner if you can. Different foods affect different people in different ways, but these are some key things I've learnt:

  • Plain Weet-Bix (a cereal with effectively no sugar [~2.5%]) and low-fat milk will send my blood sugar soaring immediately after breakfast. It is classified as a medium-GI food.
  • Protein shakes have also been cut out entirely, despite there being no sugar in the protein powder itself. 200mL of milk and a small scoop of ice-cream is enough to raise sugar levels fast.
  • Low-GI bread is a lifesaver. Two slices of Lo-GI bread from Bakers Delight has replaced Weet-Bix as my breakfast, and this has a noticeably positive impact on my blood sugar. I rarely spike after breakfast, and if I do, it's to ~9mmol/L, instead of 14mmol/L.

Choosing low-GI foods where possible will help to stabilise your blood sugar levels as these foods release energy slower over a longer period, which is more aligned with how insulin acts in your body. I'd also recommend not eating too much carbohydrate in a short space of time, as it's harder to guess carb content and the effect it'll have on your body. Ideally, you won't see a noticeable spike in your blood sugar after eating, but the ideal is rarely possible. The next best thing is to minimise the spike, and that can be done through a combination of giving insulin early enough, not overeating carbs, and choosing low-GI food.

The sensor

There are a few things worth noting about the sensor itself that would've been handy to know from the beginning.

  • The Dexcom CGM sensor is meant to last seven days. I've had it last for less time and fail to give readings (fortunately Dexcom were great about this and offered a replacement), but also considerably more - up to 14 days. I don't suggest leaving it in longer the recommended seven days, but note I had success the one time I tried it. I've only been able to try it once as often the tape has started to peel after 5 or 6 days, so the sensor is ready to be removed on day 7.
  • If you're inserting the sensor in your stomach, it's most likely that the top of the tape (closest to your chest) will peel first, so when fixing the tape, I'd recommend sealing the top edge first to ensure it's stuck in place.
  • Inserting the sensor doesn't hurt, so don't be afraid. This is a case of do as I say, not as I do - years of changing insulin pump sets has me conditioned to expect pain far too often. Surprisingly, the Dexcom sensor insertion is completely painless. There's only been once where I've found it more noticeable than a tickle, but even then it couldn't be felt after a few minutes. The insertion device is quite large and can be intimidating, but it isn't as painful as it seems.

Sanity (check)

I'm the first person to praise the convenience and luxuries afforded by having an Apple Watch. The potential of the Apple Watch as a health and fitness device is truly unlimited. A long-term hope is that the Apple Watch can perform non-invasive blood glucose monitoring, but until that day we've got invasive solutions. Dexcom's integration with both iOS and watchOS is impressive. The apps are reliable, and that's exactly what you want from a medical device. The Dexcom app for Apple Watch supports a "complication" - this means it's possible to view your blood glucose reading in real-time on the face of your Apple Watch, with no need to open the watch app to see this data. At first, I thought there could be no better feature. After a while, I realised it's unhealthy to be glancing at my watch every five minutes to get an update on my blood glucose level. Focusing on this constantly, and anxiously watching it rise or fall, is no good for anyone. You survived up until now without such frequent updates, so you'll be okay to hide the complication. Opening the watch app every hour or so should still be enough for you to see significant benefit from wearing a CGM without going insane. Again, this is a case of do as I say, not as I do. I'm a lot better at not constantly checking my watch than even this time last month, but it's still more of a distraction than I'd like it to be.

Take a break

Continuous glucose monitoring is, on the whole, fantastic. That doesn't mean it isn't overwhelming at times. There have been many occasions where I've thought it's more trouble than it's worth. Since, things have settled down mainly thanks to bolusing early, and trying to get my levels stable before sleeping. If you feel overwhelmed, I encourage you to take a few days off from wearing it. A great time for this is in between taking out the sensor and putting in a new one. There's nothing wrong with going back to doing things the old way for a while. Sure, your levels might spike, but that's been happening for years, and at least you won't be anxious as you watch your BGL climb after a meal. You'll know when you're ready to put it back in. CGM has more of a learning curve than beginning to use an insulin pump does, and like an insulin pump isn't a device for everyone.

Learning experience

Everything mentioned thus far is something that I've learnt from experience with the CGM. It's only been a couple of months, and I'm sure that the learning will continue to be plentiful for a long time to come. Ultimately the best way to know what works for you is to try yourself. Things won't work perfectly at first. I could not have imagined how frustrated I would be by the alarms after a few weeks of wearing the Dexcom.

What I'd like to see

I'm looking forward to an update to the Dexcom Apple Watch app which brings the ability for the Dexcom to send data directly to an Apple Watch. Currently, your phone must be in range of the Dexcom to receive updates, which are pushed from the phone to the watch. As of watchOS 4, it is possible for a Bluetooth health device to send data directly to the Apple Watch, and Dexcom have said they will support this feature.

I'd also really like to see granular control of the alerts. There's a lot that could be improved here, including:

  • Make it clear that by acknowledging an alarm in the iOS app, it will be silenced. I spent days thinking it was impossible to silence alarms, and that I was stuck with being woken every five minutes until my blood sugar rose high enough to stop the alerts.
  • Time of day settings. Living in constant fear that your phone will sound an uncontrollable alert is no fun. People have occasions where they don't want to be alerted to things - at work, in meetings, at the cinema, etc. Silent alerts are possible for all but critical low alerts on the Dexcom. This is a start but not perfect, as you then have to remember to turn them on again or else you won't be alerted when you actually want to be - such as overnight. Almost 17 years of diabetes means that if I'm awake, I can tell with 99% accuracy that my blood sugar is low or high. How high, or how low? Who knows, that's what the Dexcom (and previously, finger-pricks) are for, but if I'm awake I'll be able to feel the onset of low or high blood sugar. I'd love to be able to tell the Dexcom to send audio alerts between 10 pm and 6 am, but no other time. Silent notifications to my Apple Watch and iPhone will suffice the other 16 hours of the day.
  • To extend on the above, there's the concept of "Low" blood sugar in the Dexcom app. This value is defined by the user (I have mine set to 3.7mmol/L), and anything under this reading will trigger an alert. There's also an "urgent low" alarm - set to 3.1mmol/L - which can't be changed, nor silenced under any circumstances. It's a long shot, and there are other things which should be a priority, but I'd like to see smarter use of these settings based on a wake-up alarm. For example, I absolutely should be alerted to a level of 3.6mmol/L at 2 am. However, if my BGL drops to 3.6mmol/L at 5:30 am, and the Dexcom knows my alarm is set to go off in the next 30 minutes, the fact that the low isn't "urgent" means it doesn't need to wake me. I have no issue with it waking me at any time if the level is considered an urgent low, of course. This is simply something I'd like, and I realise everyone would have a different preference.
  • On a similar note, a true wildcard feature would be integration with a sleep tracker on the Apple Watch (AutoWake?). This could mean that if your blood sugar was low and steady, but not falling nor urgently low, it would wait until the end of a sleep cycle to wake you. Let me tell you, Dexcom shows no mercy and will wake you 40 mins after falling asleep if it has to. That is not a time one would want to be woken if it can be avoided.

Again, these business rules are tricky to decide, and this is no easy task to tackle, but in a world where Dexcom have infinite time and resources to develop their mobile apps, I'd like to see it happen. As a general rule, fewer app settings are better, but not for a medical device like the Dexcom, which plays such an important role in the life of the wearer. Fine-grain control is exactly what's needed here, and I find the existing control over alerts to be frustratingly limiting.


Continuous glucose monitoring can benefit every person with diabetes in a slightly different way. For a young child who may not have yet developed the ability to detect low blood sugar, CGM does this for them. For that child's parents, they can send their child off to school knowing that the CGM will catch irregular blood sugar and alert the child sooner than a teacher might notice the child's pale face and scattered concentration, which are both indicators of low blood sugar. For someone my age, CGM is about the freedom and flexibility of not having to carry a blood glucose monitor everywhere I go, but more importantly, it's about smoothing the fluctuations in my blood sugar levels leading to better control which will (hopefully) mean fewer complications from diabetes later in life. For someone prone to fainting when their blood sugar falls, CGM is about saving their life, be it overnight, or just one afternoon while excitedly watching the footy and not realising their BGL has dropped. CGM has infinite potential to benefit people with diabetes, as well as those without it. Learning what works best for each individual takes time, and is no small task. Had I known the tips above this time two months ago, I would've had a much easier time using a CGM in the beginning, and I hope that someone new to using CGM finds the tips to be beneficial.

Overview: AutoWake 1.0

AutoWake has hit the App Store. It's the first haptic smart alarm for Apple Watch. AutoWake is developed by David Walsh, a self-confessed Objective-C lover, and maker of other popular health and wellbeing apps for the Apple Watch; HeartWatch, and AutoSleep

The idea is simple. AutoWake is an alarm that wakes you in a lighter phase of sleep. The result? You feel less tired and groggy upon waking. Similar apps have existed for the iPhone for years. They require you to sleep with your phone on your bed, so they can detect motion as you sleep. AutoWake is the first to bring this to Apple Watch. I've been using it for a few months and have found it to work well.

You configure AutoWake by choosing the time you wish to wake up by in the watch app. The alarm will go off up to either 15 or 30 minutes before that time (it's up to you), depending on your phase of sleep. AutoWake doesn't need to be open on the watch to work. However, you must have the AutoWake complication active on the watch face of your choice. I find either the extra large or the modular face work well as they both offer large countdown timers. AutoWake communicates with its iPhone app to work out an appropriate time to wake you. This means AutoWake also has to be running in the background on your iPhone. You can't force-quit the app as it needs to be active. You'll need to keep an active connection between your phone and watch, so neither can be in aeroplane mode.

It wakes you up with a haptic alarm - like the alarm app built into watchOS, but with a more subtle and comfortable vibration. Should this fail, AutoWake will fall back and wake you up with audio from the iPhone app. AutoWake also triggers a heart rate reading in the seconds before it wakes you up, and shows it to you once you silence the alarm. Waking heart rate is a good indication of overall heart health, and AutoWake ties in with another of David's apps, AutoSleep, to make use of this data.

Unlike almost every other alarm app, AutoWake doesn't have a snooze function. There's no dozing off after dismissing the alarm. After giving it some thought, it makes sense. If AutoWake works correctly and wakes you up in a lighter phase of sleep, you should wake feeling less groggy and more likely to get up straight away.


There are a few apps that have had success due to the personality and character of the app. Carrot Weather is one that comes to mind. AutoWake also has subtle hints of personality which add to the overall experience. You can choose a name that AutoWake will refer to you as, and from there, its audio alerts will refer to you by your name. It's a small touch, but it makes a difference. I've got my name set to, "Egghead," and it never fails to amuse me when my phone says, "Sleep well, Egghead!" after setting the alarm.

AutoWake is an app I've wanted to exist for quite a while, and I'm delighted that the initial version works as well as it does. AutoWake is available for a small upfront cost on the App Store, and is worth every cent.

AirPods - One Year On

AirPods, Apple's take on truly wireless earphones, have been out in the world for just over a year now. They were plagued with 4-6 week wait times right from the initial launch. These shipping delays continued throughout the year, and are now affecting 2017 Christmas holiday shoppers. Whatever way you look at it Apple just isn't able to make enough to meet demand. Whether this is because they're difficult to manufacture, or because demand is higher than expected, no one is sure. One thing is certain, however. AirPods are popular. You can't walk a block through the Sydney CBD without seeing someone wearing a pair, and it isn't uncommon for me to not be the only one on the bus wearing them. Alongside the Apple Watch Series 3, AirPods are my favourite Apple product released in years.

Now, one year on, I want to look back on what I wrote in my AirPods review and explore how my initial impressions have either changed or remained the same.

These are more than special earphones. They’re a new category of wearable device.

I still believe that AirPods have the potential to be considered a wearable device, and not just a pair of earphones. Over the last year thanks to software updates, transitioning the connection of AirPods between devices (iPhone, to Apple Watch, to Mac, to Apple TV) is more seamless than ever. If I'm wearing them, it doesn't matter if I press play on audio on my phone or watch, the AirPods intelligently will connect to whatever device is best. This has other implications, such as always being able to communicate with Siri. While wearing AirPods, I know I can activate Siri discreetly on my Apple Watch, and talk as though I was holding my phone near my face.

They haven’t once felt like they’re going to fall out and this includes while at the gym doing all of my regular exercises including running, weights, pull-ups, push-ups, sit-ups; you name it. They’re hardly noticeable in the ear.

It's easy to forget you're wearing AirPods. They remain as lightweight and comfortable as ever (though the comfort factor isn't the same for everyone), and despite not having perfect sound quality, the convenience of the AirPods design is enough to make me not want to leave the house with any other pair of earphones.

Although battery life isn’t fantastic for “wireless” earphones, my early usage suggests 5-6 hours on a single charge - in line with Apple’s estimates.

After using AirPods for a year, I'm convinced that the battery life does not matter. I'm not sure how long they last on a single charge anymore; it could be 2 hours, or it could be 7. It doesn't matter. There is almost never a situation in which I go more than 90 mins between putting them back in the case to charge. I've never found the battery life not to be good enough. Sure, a few hours may not sound like a lot, but how frequently are you using them continuously for that length of time? Even popping them back in the case while you visit the bathroom at work is enough to top them up for a few more hours of use.

Having to charge so frequently might sound in conflict with what I said earlier about wearing them constantly.

Still true. While battery life is good enough for day-to-day audio listening, the idea of AirPods as wearable tech won't be taken seriously as such until they can last in your ears all day should you need them to.

Siri on AirPods has been a disappointment for me so far. The way to active it is to double tap on either bud and then talk.

I've found the best way to talk to Siri with AirPods in is to activate it from the Apple Watch by pressing the Digital Crown. It's going to work every time.

To truly be free from your phone while using AirPods, a smartwatch with audio controls of some kind is necessary.

This is true more than ever. Controlling the AirPods with only a phone is still clunky, but using a smartwatch makes this a lot easier. Now that the Apple Watch Series 3 has a cellular/4G connection, the combination of AirPods + Apple Watch is even better. You can now leave the house without a phone and listen to music while walking around or exercising, while also being able to take phone calls, and dictate messages. It's a powerful combination, and having the AirPods with the cellular watch makes the experience notably better.

We've seen some small improvements in the last year to both the software controlling AirPods, and to the hardware they connect to. Improvements to the way AirPods handle connecting to different devices and new hardware such as the Apple Watch Series 3 take away some of the hassles I addressed in last year's review. There are a few improvements I'd like to see to AirPods going forward. The first is better sound quality. The sound quality of AirPods isn't bad by any means, but there are times when higher quality audio is appreciated, and not having to find another pair of earphones in these situations would be nice. Secondly, water resistance. iPhone and Apple Watch are both water resistant enough that if you're stuck in the rain with them it isn't an issue. It would be nice if AirPods were also water resistant. I've heard that they do survive submersion in water, but until Apple promote water resistance as a feature themselves, I'm reluctant to let the AirPods get wet. Finally, I'd like to see a dark (space?) grey or black colour offering - purely for cosmetic reasons. I know that Apple are unlikely to stray from their distinctive white earbud design, but the new Space Grey peripherals that come with iMac Pro show that they are open to mixing things up.

CGM Diaries: Week 1

I've now spent a week living with a continuous glucose monitor (CGM). I've got a lot of thoughts, but it's safe to say that it's nothing short of amazing. CGM is a transformative technology for people with type 1 diabetes. I've been amazed by the accuracy of the sensor, how unobtrusive the design is, and how useful it has become to know my almost real-time glucose level. I wrote about it extensively in the first few days, which you can read here, here, and here. I'll try not to recap any of that in this post.

What I've learnt

It's been quite impressive to witness glucose levels spiking right after certain meals, and not others. While this has undauntedly been happening for years, it's the type of things you don't notice when you're taking intermittent glucose readings. It can be frustrating to watch the reading rise while knowing it might be an hour before it starts to fall again. I Tweeted saying that I'm considering not eating carbs again, mainly to avoid these spikes. The Tweet was hyperbole, but it has made me start to reconsider certain food choices. For example, a bowl of Weet-Bix in the morning will likely be replaced with toast as it doesn't have such a negative impact on my levels. It's also been positive to learn that the Dexcom CGM is accurate. It requires two manual calibrations per day, and most of these have given readings within 0.5 mmol/L of what the Dexcom is showing.

What's useful

Near real-time glucose data is truly transformative. It takes the guesswork out of managing diabetes and means I can choose to take action on my glucose levels at almost any time. Feeling a bit on the high side? A quick glance at the watch will either confirm or disprove this feeling, and means I can take action if necessary. It's also reassuring to be able to check my Apple Watch in the middle of the night and know I'll get an instant reading. There are times when the reading is not bad enough to have triggered an alarm, but the fact I'm half awake means I can glance at the reading and decide whether to give insulin. Despite my dislike for alarms on the phone during the day, they're great overnight. It's useful to me alerted overnight when my levels aren't great. While not a life-saving advantage, another is being able to leave the manual finger pricker at home. It's one less thing to carry and worry about, and one less thing to awkwardly take out and use in public. With a glance at my wrist, I can discreetly check my glucose level, and move on with life.

The sensor

The physical design of the sensor is bulky, but despite this, it is less noticeable in most situations than the smaller connection for the cannula of an insulin pump. It's easy to brush against, especially when placed in the stomach, but the tape holding it in place is strong, and it isn't easy to knock out. It's also more comfortable than the pump connection, as it's hardly noticeable when sleeping. I did mention last week that it is slightly uncomfortable in the car as it brushes against the seat belt, and also while running. The former is still true, the latter not so much. Perhaps it just took some getting used to. I've also spent some time swimming at the beach these last few days, and it hasn't been an issue there either.

Changing the sensor

Since the sensor had been in for a week, it was time to change it this morning. The Dexcom app alerted me to this by sending multiple notifications this morning informing me the sensor would cease to work at precisely 10:20 am, and that it was time to replace it. There are two parts to the CGM. There's the sensor itself which sits just underneath the skin. This needs to be removed every week and replaced. There's also the transmitter, which is connected to the sensor. It sits on the outside and is what crunches the data, and sends it back to the phone. The transmitter lasts about three months, so it is retained and connected to the next sensor. Pulling it out is straightforward enough. Once the tape around the edges is removed, the sensor slides out easily. Unlike an insulin pump cannula, it hasn't left much of a mark on the skin. Once it's out, the insertion process begins again (on the other side of the stomach). As was the case with the initial insertion, it requires two hours for the new sensor to "warm up." Once that time has elapsed, two consecutive manual blood glucose readings are needed to calibrate the sensor, and then the CGM is back in business.

Time away

It's not always practical to be within Bluetooth range of your phone. It's happened a few times during the last week that I've not been nearby my phone for a few hours at a time. The transmitter simply stores a history of these readings every five minutes as it otherwise would, and sends them across with the first sync after your phone and Dexcom establish a connection again. It works reliably, and to my knowledge hasn't missed a single reading all week.

That's been the first week. I am enjoying having access to the real-time data a CGM provides, and the way that it can help me make informed choices when trying to control my glucose levels. The Dexcom app now lives on the home screen of my phone, and as a complication on my Apple Watch face. It's incredibly useful to have access to this information, and Dexcom's app is impressively reliable.

If you're reading this and reside in Australia, I'd really appreciate it if you took a moment to fill out a form here. It sends a letter to your local member of parliament requesting funding for CGM technology for everyone in Australia who needs it, and not just those under 21 years of age 21 as is currently the case. I wrote a letter and sent it tonight, and would really appreciate support from others. If you've got any questions, I'd be more than happy to answer. You can ask me question via the form here, or on Twitter.

CGM Diaries: Day 3

Day three. I'm starting to get used to the CGM and learn more about how it's going to fit into my life. Today was a good test for it, as I was out of the house for an extended period.

This morning began with the first run I've been on since getting the Dexcom. Having an Apple Watch with a built-in 4G connection meant I didn't take my phone. A side effect of this was not being able to see my glucose levels while running, as the Dexcom connects to the phone but not to the Apple Watch. This will change as a result of watchOS 4 and changes to CoreBluetooth, but as I type this those features aren't supported yet.

The Dexcom sensor is comfortable enough for day-to-day activities. I haven't been able to feel it when at the gym, or when sleeping (which is what I was most concerned about. It has brushed up against the seatbelt in the car which can get uncomfortable, but it's no big deal. Where it's been most uncomfortable was on this morning's run. There's no other way to describe it other than it felt heavy. I've not felt this way about an insulin pump set, but the Dexcom is absolutely noticeable - and somewhat uncomfortable - while running. Again, not a huge issue, but it's something to note.

After years of being trained to complete regular "finger pricks" around lunch time, losing this mindset is taking some time. With the CGM, I can just eat. As strange as that sounds it's true. There's no longer a prerequisite to eating. Similarly, earlier today I found myself feeling a rise in my blood sugar. It was only minor, and usually I wouldn't worry about it. With the CGM, I was able to glance at my wrist, note that it was slightly higher than it should be, and give a dose of insulin through the pump. Not having to draw blood to get this information is helpful.

As I've mentioned previously, it is recommended to calibrate the Dexcom sensor with a manual "finger prick" every 12 hours. Being out of the house for so long today meant that these two calibrations would occur about 16 hours apart. That hasn't stopped the Dexcom app from sending me a notification every five minutes since 6 pm this evening reminding me to, "Enter BGL meter value." There seems to be no way to clear this without entering a false calibration - which I'm reluctant to do. On the positive side, these notifications aren't making audio alerts. Another positive is that all of the calibrations so far, except one, have been within +/-0.5mmol/L of the current Dexcom sensor reading. It's reassuring to know that it's accurate.

Today was the best day I've had so far for learning what makes the CGM useful. Highs and lows are unpreventable for someone with type 1 diabetes, but a CGM ensures you're on top of these swings and can help you recover from them faster. The highs won't be so high. Nor the lows so low. It's about the convenience of leaving your blood glucose monitor at home for the day. Did I mention? I haven't seen the thing since seven this morning - which is almost certainly the longest time I've spent away from one in over 16 years.

CGM Diaries: Day 2

I feel the need to begin by stating that this is in no way a complaint about the Dexcom G5 continuous blood glucose monitor and that I am extremely fortunate to be wearing such a device that gives me continuous, real-time data. It works well. Being able to see this data in real time will undoubtedly lead to better overall control. It's already saved a hypo. This post is simply what I've discovered when trying to write software based on the data provided by the Dexcom.

As a software developer, the thought of the data collected by the Dexcom is exciting. The Dexcom iOS app works well but isn't perfect. That's okay as long as there's access to raw data. In theory, access to all of the readings off of the sensor would allow me to build an entirely custom app for viewing real-time glucose readings on both iPhone and Apple Watch. This theoretical custom app would also include support for my preferred Apple Watch complication, as well as more granular control over notification and particularly the sounds they make. Another possibility would be a custom companion app, so that my parents could check in with my glucose level overnight. There are countless possibilities.


My first thought was to build something that pulls data from HealthKit and work with it that way. The Dexcom app currently writes data to HealthKit at a delay of an almost-perfect three hours. I addressed that in yesterday's post. While that is okay for an app that analyses longer-term data and trends, it isn't helpful for the projects I had in mind for today, with the goal being to use data that's as real-time as possible.

Dexcom API

A quick Google search this morning for "dexcom api" lead me to realise they do have a way for this data to be accessed by third parties, so I decided to play around with it. Many hours later (too many of which spent getting the authentication right), I wondered why the simple app I'd built to return data captured in a given period wasn't working. That's when I came across the following on the Dexcom website.


That explained why today's efforts were failing. It's disappointing as a developer, but I'm sure there are valid explanations as to why. As an FDA approved device, there are processes in place, and lots of regulation they have to adhere to before anything gets done. I can also confirm that this problem can't be addressed by simply changing your Dexcom account address to a United States one.

Where to from here

I'm a little deterred knowing that there isn't a reliable way to access real-time data from the Dexcom sensor. It doesn't matter much - the official Dexcom app works reliably and is enough for most people most of the time. A possible next step is to try and read data straight from the Dexcom sensor via Bluetooth. Some quick searching earlier this evening tells me this may be possible, but that's a project for another day.

CGM Diaries: Day 1

Following on from yesterday's post, today was CGM pickup day. This involved visiting the hospital to collect the first batch of supplies for the CGM, as well as set it up, and learn how to use it. This is more of a "first impressions" post, as it will take a while to be able to assess its usefulness in managing glucose levels overall.

The smaller box contains the Dexcom transmitter. The larger box contains the sets.&nbsp;

The smaller box contains the Dexcom transmitter. The larger box contains the sets. 


Surprisingly simple, there are two parts to the Dexcom G5 CGM. There's the transmitter (shown above as the smaller of the two boxes), and the "sets" - the piece holding the cannula that attaches to your skin. The Dexcom iOS app has a straightforward onboarding process which ends with you linking the transmitter device by scanning a barcode on the back of the box.

This is used to fix the set to the body. It looks scarier than it is.&nbsp;

This is used to fix the set to the body. It looks scarier than it is. 


Sensor insertion

Nearly lifetime of needles, nor over eight years of inserting cannulas for an insulin pump meant I felt calm when seeing the insertion device. It worked fine and fortunately didn't hurt, but that doesn't mean it wasn't intimidating. You can wear the set either in your stomach or on the back of your arm. I choose stomach, as I'm comfortable with putting the sets for my insulin pump there and figured it's a safe option. Once it's in, you clip the transmitter device into the plastic enclosure of the set where it sits for the next week. The transmitter lasts three months, while the sets are swapped every week.

Physical size

It's bulky. See the photos above. It's about twice as thick as the insulin pump sets I'm used to. It's not uncomfortable, but my biggest concern is that it'll be easy to knock out. For reference, sensor and the set combined are about a thick as the width of my index finger.


Getting started

Once the sensor is inserted, it takes two hours to warm up. From there, it asks you to do two manual blood glucose readings, one after the other, to calibrate the sensor. You input these into the Dexcom app, and from there it gives you your first reading. After that, it senses your glucose level every five minutes and sends that reading back to the phone. Interestingly enough, Dexcom makes the only CGM sensor that is accurate enough to trust as a replacement for blood readings. Despite that, two manual blood readings are still required per day to keep the sensor calibrated.


The iOS app

The iOS app is fairly simplistic. It shows you your current reading, along with an arrow indicating the trend of the readings. It's worth pointing out that, for those who care, the iOS app is still running at iPhone 5 resolution - not yet updated for 4.7" and 5.5" displays, let alone the 5.8" screen size of iPhone X.


Notification alerts

The Dexcom app offers real-time notification alerts for glucose levels that are either too high or too low. These somehow bypass silent mode, do not disturb mode, and the system volume level on iOS. I've received a few of these notifications already (don't judge - the CGM should help reduce the number of poor readings I have) and it's safe to say they're extremely annoying. My phone has stayed in silent mode from the second I got a smartwatch four years ago, and I don't like the fact that notifications are making noise again. More granular control over this would be appreciated. It may be useful overnight to alert me to hypo (low) glucose levels, but I wish there was a way to silence them. A tap on the wrist from the Apple Watch is all I need to see an alert and action it.


Apple Watch complications

For a variety of reasons that I won't go into here, I've used the "Simple" Apple Watch face (shown in the first image above) almost every day for two years. I am also of the opinion that having an Apple Watch and a Dexcom CGM means you are obliged to use the complication to get your BGL at a glance. Unfortunately, the Dexcom complication doesn't support the Simple watch face. The closest alternative is "Utility" - shown in the second image above. It means I lose having my step count on the watch face, as there's space for one less complication, but I think that's a worthwhile tradeoff for now. The only watch face that allows me to have the Dexcom complication as well the other complications I'm used to is "Modular" (third image above) but I'm not a huge fan of that one. I might use it as my overnight sleeping watch face but will try to avoid it during the day. It's too early to tell for sure, but the complication seems to update every 10 minutes, which lines up with every second reading recorded by the Dexcom sensor, so it's frequent enough. Occasionally I have noticed that it fails to update, and instead shows three dashes "---" (shown in the fourth screenshot above).


HealthKit sync

Another reason for choosing the Dexcom CGM, other than it being the most accurate, was that it's the only one to sync to a phone. If you have an iPhone, not only does it sync to the Dexcom app on your phone, but also optionally can write the data to HealthKit. This is perhaps the most strange thing I've discovered about the Dexcom so far. The Health screen reads, "Dexcom G5 Mobile information posts to Health with a three hour delay." My first thought upon reading this was that it only writes to HealthKit every three hours - i.e. eight times per day, maybe in an attempt to save battery?


As far as I've been able to discover, the Dexcom app writes to HealthKit every five minutes but writes the reading from three hours ago. I'm not sure why this is, and I'll continue to try and find out why. It feels arbitrary. As can be seen in the above screenshots, a reading recorded at 2:29 pm was written to Health at 5:29 pm, and a reading from 2:34 pm was written to health at 5:34 pm.

Wrapping up

I've still got a lot to learn about the Dexcom CGM. The best way to use it, how to interpret results and trends, and how it fits into my life all remains to be seen. Some sections may have sounded a bit like a complaint, but I assure you it's just an expression of my initial impressions. I am in no way complaining about the bulkiness of it, the missing "Simple" complication, nor HealthKit sync. I'm in a very fortunate position to have a CGM, and these are simply the things that have stuck out to me that I wanted to share after six hours of use.

CGM Diaries: Day 0

Continuous glucose monitoring, so I'm told, is life-changing technology for people with type 1 diabetes. I spoke to someone last week who told me her HbA1c result (essentially an average blood glucose level over three months) was down to 6.1 mmol/L from 8.1 mmol/L. That's 110 mg/dL and 146 mg/dL respectively. I've heard similar results from others. That is no small improvement, and on top of feeling better in day-to-day life, it dramatically reduces the chance of developing complications from diabetes later in life.

The range of continuous glucose monitors (CGM's) available now are all invasive, meaning they puncture the skin to work. I've written before about what non-invasive blood glucose monitoring would mean for people both with and without diabetes. The idea excites me beyond belief. However, it may still be years away, and for now, the choice is whether someone sees the benefits of CGM enough to accept the tradeoffs. If someone with diabetes is also wearing an insulin pump, expecting them to live with another cannula in their body (generally either in the stomach or back of the arm) may be a dealbreaker.

Inconvenience aside, the cost is probably the most significant factor preventing more people from wearing the current CGM's available. Diabetes Australia says the cost of CGM, including sensors, is around $5000 per year. That's no small amount of money and puts the possibility of wearing a CGM out of reach for many people.

With some notable exceptions, it's nice when an elected Government follows through with an election promise. The current Australian Federal Government committed to wholly subsidising the cost of CGM devices for Australian's with type 1 diabetes who are under the age of 21. This is thanks to tireless lobbying from the Danii Foundation. Fortunately, I am eligible for the subsidy for the next 11 months.

After speaking to the doctor at my last checkup, she agreed a CGM would be beneficial, and I'm scheduled to have have one set up tomorrow (4th December, 2017). The CGM model is the Dexcom G5, which was recommended as it's the most accurate, and can replace all but two "finger-pricks" per day for checking blood sugar. It also transmits data via Bluetooth, and as a result, will sync the data to HealthKit on my iPhone and Apple Watch. The ability to store this data reliably for future reference is a definite advantage.

This is an exciting time when the possibilities are considered. Improved control and management of blood glucose levels will almost certainly lead to advantages I can't even think of at the moment. Because of the integration with iPhone, Apple Watch, and HealthKit, I also plan on writing about it on this blog. Those posts will likely focus on the integration between the Dexcom sensor and this technology, as opposed to how CGM is affecting the management of diabetes and my blood glucose levels. On the other hand, a bulky sensor may be deemed not worth the tradeoff. I'm curious to find out.

While I've got your attention on this topic, we're still raising money for JDRF. Their research leads the way in working towards a cure for type 1 diabetes. Any amount you've got to give goes is greatly appreciated. You can read more, and donate here.

Experimenting with App Store Search Ads

What are Search Ads

App Store Search Ads have been around since October of 2016. Apple describes them as, "An efficient and easy way to promote your app at the top of relevant App Store search results." They were only shown in the U.S. App Store up until April of 2017 when they were introduced to the UK, Australia, and New Zealand. Since then, they've been added to the Canadian, Mexican, and Swiss App Store, bringing the total number of App Store markets with Search Ads to 7.

Here's how Petty's Search Ads look on the App Store

Here's how Petty's Search Ads look on the App Store



I make Petty which is an app for iOS and Android that helps New South Wales (NSW) drivers find affordable petrol nearby. Petty came about because I thought the NSW Government's petrol price dataset looked cool and knew that it was the most accurate one around. At that stage the best tool one could use to view prices from the same database was to use a website, called FuelCheck, run by the NSW State Government. I thought the idea of a decent native app, as opposed to having to visit frequently was appealing.


About a month ago the NSW Government launched FuelCheck in the form of a mobile app for iOS and Android. Its release was inevitable. As best I could tell, it "soft launched" on the App Store and Google Play a few weeks prior, but the hard launch date was the 11th of October, 2017.

The first I heard about the launch was in a Tweet by the NSW Premier, Gladys Berejiklian.

Naturally, there was a lot of attention given to FuelCheck. Petty and FuelCheck are two different apps and Petty has things to offer that FuelCheck doesn't, including showing the time prices were last updated at nearby stations, an Apple Watch app, notification centre "Today" widget, and - as I Tweeted at the time - assurance that you aren't using something made by the government.

It was half-jokingly suggested by a friend of the blog (who didn't get a say in their friend of the blog status) Pat Murray to buy Search Ads on FuelCheck's search terms. That evening, I set up an ad campaign and did precisely that.

Search Ads for Petty

To provide some context, Petty is a free app with optional in-app purchases (IAP). Most of its (insignificant) revenue comes from the IAP to unlock "premium" mode - removing ads and getting extra features. The rest is from an optional tip jar. The money made on display ads is so small it might as well be a rounding error. It's worth noting that any money or dollar figures mentioned are in Australian dollars (which, for the fun-fact enthusiasts among you, is the fifth most traded currency. The ads for Petty were only shown to customers who have not previously downloaded the app, and those who were located in Sydney, Australia.

The ad campaign

I hadn't run a Search Ads campaign since Apple gave $100 in free credit at launch to every developer encouraging them to try it out. Early on it was established that I was only willing to throw $30 at the ad campaign and that the ads were going to run on the iOS App Store only despite there also being an Android version of Petty. $30 sounded like a nice number - small enough that it didn't matter if it resulted in zero additional revenue, but enough to gather some data with. I expected the ad campaign to be over sooner than it was, as maximum daily spend was set to $7.00. It took almost a full month for the $30 budget to be exhausted.

Here's a breakdown of the spend per week

Here's a breakdown of the spend per week


The ad campaign finished with 927 ad impressions, and 168 taps on those ads which converted into 101 installations of the app. This gives a tap through rate (TTR) of 18.12%, and a conversion rate (CR) of 60.12%. I'm particularly impressed with the CR which shows that a majority of people pressing the ad were interested, and went on to download it. There isn't much public data I can compare this to, but it's slightly higher than what early results for Search Ads showed - a good sign overall.


The most important metric when running an online ad campaign for an app is the cost per acquisition (CPA) of a customer. This campaign saw an average CPA of $0.30, which is lower than I expected, even for a free app.

CPA is an important metric because it tells you whether or not your campaign is worthwhile. The marginal cost of an additional customer of your app is almost zero. In a simplistic model, take average cost per customer (such as data, and server expenses) away from average revenue per customer, and you're left with a bit more than the amount you can afford to spend to acquire a new customer.

These keywords were the only three to see meaningful results&nbsp;

These keywords were the only three to see meaningful results 


The ad campaign began with only a few keywords: petrol prices, fuelcheck, fuel check, and fuel watch. Throughout the month the ads were running, I increased the number of keywords that ads were running against. At the end of the campaign, only three keywords generated more than 100 impressions, and more than 5 installs each. They were: petrol prices, petrol, and fuel watch.


Interestingly enough, ads for Petty did not score so much as a single impression on either "fuelcheck" or "fuel check" - the two most important keywords set. I know the Government themselves were bidding directly on that keyword, as were 7-Eleven with their fuel app, and their default CPT bid was likely a lot higher than the $2.00 I set for Petty ads.

After a few days, "fuel watch" was trending, but not, "fuelcheck."

After a few days, "fuel watch" was trending, but not, "fuelcheck."


That means these ads weren't shown to people who were visiting the App Store and searching for FuelCheck directly. The ads likely were shown to people who had heard about the Government's app but weren't sure what it was called. It is interesting that a trending search term on the App Store only three days after the launch of FuelCheck was "fuel watch." It trended for about 24 hours, and as you can see from the data above, that was the single most popular search term for Petty's ads during the campaign.

Wrapping up

There are a few key points to take away from this experiment. Search Ads on the App Store work. Unlike Facebook or Google Search ads, where you pay $20 only to get the email, "Your campaign has ended, and your page has ONE new like!" Your mileage may vary, but the $30 I spent resulted in just over 100 new customers, at a cost to me of $0.30 per customer. As far as CPA goes, it was an effective means of advertising. Another thing to take out of this is that you don't need to spend a lot of money to see results. $30 was enough in this instance, and it lasted nearly a month. $20 probably would've been just as fine. Play around with different ads and keywords to figure out what works for you and your app. Run an inexpensive campaign to figure out what your CPA is, and go from there. I also learnt it's difficult to outbid the "big guys." They're almost certainly going to bid higher on the popular terms, such as "FuelCheck," so it's important to find some moderately popular, niche keywords ("fuel watch," in this case) to see results.

There's more data that you can take from a Search Ads campaign and more detailed analysis to be done on the data than I've written here. I hope this provides a good overview of what to expect when you run a Search Ads campaign and how it can be an inexpensive way to attract more customers to download your app.

iPad Productivity at Uni

I think a lot about productivity, and how to be more efficient when working. The most prominent challenge for me relates to University work. I've always found it easier to achieve "deeper work" (more extended, uninterrupted periods of working time) when working on side projects than when doing things for Uni. This will be a short post, but I'm writing it here as opposed to on Twitter because Twitter dot com doesn't need another Tweetstorm.

I'm in an arguably lousy habit of working on side projects while at Uni. It begins when I pull my laptop out on the bus, start working on something, and then continue that when I get to Uni. Sometimes this means spending the first few minutes of a class wrapping up said work. Later, during the next break between classes, I'll continue. Procrastiworking (doing productive work that just isn't the work you should be doing at present) isn't inherently bad; however, it does mean I'm not working on Uni work at Uni outside of time in class. I tend to do most of my Uni work at home, and I get it all done there without issue, so I guess I'm trying to complete more while at Uni.

In a hypothetical world where I only take an iPad to Uni (as opposed to the MacBook Pro I carry now), I would probably be able to complete about 80% of the work I need to. The remainder (subjects involving programming assignments) would have to be done at home, but seeing as though I already do most of my Uni work at home that would be fine. I could take notes with an Apple Pencil, access all of my folders and documents through the OneDrive (or Files) app, and browse the Internet to conduct research. iOS on the iPad has come a long way recently and is certainly up for the challenge.

In this hypothetical world, I can see things going one of two ways. Either the iPad helps with focus at Uni, or it doesn't. Sounds obvious, right? There's no decent IDE for me to open and start working on a project with, so in theory, I'd have to do Uni work. This would also apply to time on the bus. If I pulled out my computer - in this case, an iPad - the only productive tasks I could complete would be work for Uni. The second possible outcome is that I just find another way to be distracted. More Twitter perhaps? Goodness knows I need less of that in my life. If the latter proved to be correct, it would be a net loss of productivity. There would be no procrastiworking, but no additional "real work" completed either.

No conclusion has been reached here. It was just a fun little thought experiment on my last day of classes for the year. I almost certainly won't buy an iPad for Uni, but it's fun to think about different ways of working.

Even the act of writing this was a form of procrastiworking between classes. Bring on exams. 🙃