You have probably seen me wearing a small device on my upper arm in a lot of the pictures on this website. That’s my CGM, an instrumental tool in my daily diabetes management. It’s a brilliant piece of equipment and I absolutely love it (most of the time).
CGM stands for Continuous Glucose Monitoring. This device makes it possible for me to see my blood glucose readings in (almost) real-time and track historical data. The piece of equipment you see on my arm is a small sensor with an attached transmitter. The CGM then allows me to see my blood sugar levels and how I’m trending on my phone or on the receiver that comes with the CGM.
There are currently three CGM systems available for personal use in the US:
- Medtronic Enlite
- Dexcom
- The implantable Eversense
- (there is also the Freestyle Libre, but in the US it’s not approved to send continuous data so it’s a fingerstick replacement, not a real CGM).
I got my first Medtronic CGM in December 2012 and wore it every day for 18 months before taking a break. I then ordered my first Dexcom system in August 2016, and that has been my go-to since.
There are pros and cons to all CGM systems, but since I’ve only worn the Medtronic and the Dexcom, I’ll give you my opinion on those so you can decide if it’s something that would help you manage your diabetes better.
The advantages of continuous glucose monitoring
Information
If you do manual blood sugar measurements and know your body well, you probably think you have a pretty good idea of what your sugars are up to between measurements. Well, you are most likely wrong.
I got a big surprise when I started seeing how my blood sugar actually varied throughout the day, not to mention during the night when I usually don’t test. And that’s why CGM is such an awesome tool for in-between measurements information.
All of a sudden, I could see how certain foods and activities affected my sugars over the next several hours. That information is golden! Also, being able to catch low sugars before they actually happen has significantly reduced my number of lows, not to mention reduced my consumption of glucose tablets and juice.
Management
What to do with all this new information? Well, it has not only helped me limit hypo events, but I also managed to reduce my A1C level to around 6%. I have always been pretty well-regulated, but have never been this stable before.
Of course, just slapping on a CGM won’t manage your diabetes, but the insight from it can.
I learned that if I sleep any later than 8 am before taking my morning insulin, I’ll be battling high sugars at least until noon.
I’ve learned what kind of activities will make my sugars drop FAST (that would be walking), my true insulin sensitivities throughout the day, and that I always need a minimum of ½ unit of active insulin on board before a workout.
It took time and did include a few missteps, but that’s life and that’s learning. The information made it possible for me to optimize my training, and make it easier for me to stay in a 90-144 mg/dL (~5-8 mmol/l) range when exercising.
Confidence and security
My CGM has enabled me to understand my diabetes better. It has given me more confidence in the way I manage my diabetes and has helped me achieve tangible results.
It’s also comforting to know how my sugars are trending. I will even venture out sometimes without bringing all my diabetes gear (!). I also stopped testing 10-12 times a day because I didn’t need to — the info was right there on the screen in front of me.
It enabled me to go for a walk or a hardcore gym session without fearing lows and to reach both my fitness and diabetes health goals more efficiently.
The disadvantages of continuous glucose monitoring
Accuracy
Anybody who has ever worn a CGM knows the frustration of manually testing your blood sugar and seeing that the sensor is way off. The reason behind this is that the technology just isn’t perfect yet and the sensor measures your BG based on the interstitial fluid and not the bloodstream.
Aside from the obvious problems, it can also be outright dangerous if you rely solely on the sensor readings, and ignore what your body is telling you. For example, if the CGM warnings are going off telling you that you are at 250 mg/dL (~14 mmol/L), it can be hard not to react.
I have also had to stop workouts because the sensor inaccurately told me that my BG was low or about to get low. Annoying!
Over-reliance
This is actually the main reason why I originally stopped wearing my CGM and why I take breaks once in a while.
I can have a tendency to rely on the readings and recommendations a bit too heavily. For example, if the reading said that my BG was dropping quickly, I would trust it over how I actually feel, and I think that’s a big no-no when it comes to diabetes management.
I’ve gotten a lot better at using the CGM as a data point and not the complete truth, which has made it a far better “partner”.
It’s attached to your body – Having the CGM sensor attached to my body all the time can be extremely annoying. It not very big and people don’t really notice it, but it does leave somewhat unattractive suntan marks and I scar easily.
If I wear it on my stomach it tends to get in the way when working out, so I usually wear it on my upper arm. I find that I get pretty good readings with that placement, the only issue is that it can be a little hard to get a sweaty sports bra off without ripping at the sensor.
Wearing it on my upper arm has led to some pretty cool interactions and conversations with curious people. I don’t mind, I see it as an opportunity to educate and advocate. But if it bothers you, then there are plenty of other areas to place the sensor where it’s not visible.
I wrote a post about my best CGM tips where I talk more about how to put on the sensor (with a video) and how to make it stay on.
Which CGM to choose
As mentioned, I have only tried the Medtronic and Dexcom CGMs.
I prefer the shape of the Enlite transmitter since it’s flatter and doesn’t stick out as much as the Dexcom. Being flatter means, for me, that it wouldn’t get bumped off or snagged on things. If you have a Medtronic pump, it’s almost a no-brainer to get the Enlite, since it’s integrated with the pump. That means that you see your blood sugar readings directly on the pump.
And if you have one of the two newest versions of the Medtronic pumps (530/670), they come with the new “artificial pancreas” features where the pump will stop delivering insulin when your blood sugar is low or trending low.
However, if you’re on pen therapy (MDI) like I am, the upside to the Enlite starts to diminish. I prefer the Dexcom because it sends the readings directly to my phone, and it’s now so accurate that the FDA has approved that you can dose your insulin based on your CGM readings (I still test though — guess I have trust issues).
What I do wish that the Dexcom people would improve are the alarms (high and low) that can’t be turned off. I understand that it’s a safety feature, but sometimes I’m in a meeting where I can’t have it go off and sometimes I just want to sleep and correct in the morning.
My recommendation
Would I recommend CGM to any insulin-dependent diabetic? The answer is a BIG YES, at least until you understand your body and your diabetes better. The CGM will give you knowledge about your diabetes that you have never had before, and if after a while you feel like you no longer need it, you can just stop using it.
The key for me when using my CGM is to get better at listening to both the CGM and my body. It’s a great tool, but it’s not a substitute for my own thinking and experience. It’s a great tool to have in my toolbox but it can’t stand alone.
HI, You may not be aware that there is now the “FreeStyle” Libre, Flash Glucose Monitoring System.
It was very recently approved and I have had one for two weeks. I was the first one to order it from
my pharmacy. It is “a continuous glucose monitoring device indicated for the management of diabetes
in persons 18 and older. It is designed to replace blood glucose testing for diabetes treatment decisions.”
You mentioned that there were only two systems available but now there are three that I am aware of.
Hi Sue – that’s a great comment. While the Libre system is a really cool addition to the diabetes management toolbox it’s not a CGM but rather considered a fingerstick replacement. As you know you have to “swipe” the receiver to get a reading and it doesn’t give you alarms and alerts, but as an upside, you don’t have to calibrate it.
Unfortunately when sensor was carefully removed from upper arm I was left with two abrasions and puncture marks. Maybe that’s why my Dr said it could only be left on ten days. Now I have a wound to heal I can’t imagine an arm with multiple wounds and am very disappointed.
Yikes, was that due to a Libre sensor? Almost sound like an allergic reaction?
I live in the UK and use the Abbott Libre Freestyle. For me CGM is a game changer and combined with an insulin pump provides greater flexibility especially when undertakingg extended periods of exercise. I am 57 years old living with type 1 diabetes. I have been lucky enough to take part in endurance cycling events riding across France and the knowledge CGM brings is phenomenal. However the effects of aerobic and anaerobic are counterintuitive, seeing blood glucose rise after a steep hill is spooky.
I glad the combination is a winner for you! And I really agree that sometimes watching the curve climb can be a nailbiter
I have the Dexcom G5 and am able to turn my alerts on and off, which is very helpful at night. I always keep the low alert on, but will turn off the high at night. It has had a huge impact on my life as my A1c is now where it needs to be and I’m not eating unnecessary snacks in fear of lows. My husband and I both sleep better than we have in years because we don’t worry about the lows at night. It is very pricey because I have a high deductible and I am hoping the price will come down as it becomes more mainstream.
I’m so glad to hear that CGM has been such a life changer for you. And I’d also love for the price to come down some 🙂
The only thing that you haven’t mentioned is how expensive these cgms are – in Australia nearly $800 for the system and then, supposedly over $100 a month for the ongoings – sooo important for me as a single parent to have one but with no government assistance here, it’s completely unavailable to me, I was lent one for two weeks and the amount of lows I prevented were truly life changing, it’s an amazing piece of equipment for enabling a diabetic to work their levels out.
Yes, it can be very expensive if you don’t have coverage. I don’t really dig into costs since they differ greatly across the world, and in the US it will depend on your type of insurance. But it’s such a shame that it’s so expensive since as you mention it can really help prevent lows
Interesting read. I am T2 and don’t take insulin at this point but think it’s cool to have all the real time info. Are these expensive? Could a T 2 use for education? Sometimes I need more info than I have to evaluate my choices.
Thanks for sharing. You are a great writer engaged in helping others. All the best….
Hi Paula – thank you!
If you are in the US I suggest you call the company you would like a CGM from directly and ask what it would cost you. They are not cheap, but the level of co-payment really depends on how good coverage you have. Another option would be a sensor you wear for 7-14 days and your doctor does the analysis with you (I believe it’s only Medtronic, Dexcom and Abbott that offers that). That’s not real time though, and since you’re on insulin, you might benefit more from CGM. Your endo would be a good person to discuss that option with.
Thanks so much for posting this! I am currently on the Dexacom and it’s nice to know that I am not the only one who finds you can’t turn off the alarms. Even if I correct sometimes it takes a couple hrs for me to go down and if I am sleeping or at work, I don’t want to hear the alarms.
And yes! The CGM is not always right on target! Which is annoying. But like you said it does help me not to have to keep checking my sugars all the time to see where I am at or which foods I react to.
But thanks for posting! I wouldn’t give up my Dexacom and currently have to wait for the pump. Not sure if the pump will work for me but I think my nurse will let me trial run on it. So your on Dexacom and the pen? Not the pump right.
Hi Leana,
Yes, I use pens and CGM. I think you more often find the pump+CGM combination but pens+CGM really works for me.
I hope you’ll be happy with your pump, I know so many who loves theirs
I would love to hear your reasons for using the MDI instead of the pump?
Hi Laura – whether a pump is the right choice is going to vary by the individual and for me, it’s a personal choice. I fully understand the benefits of pumps and know many who love theirs. I personally prefer a long-acting basal as background insulin rather than a rapid-acting insulin. And I’m willing to dose and test as much as needed, meaning that it’s doubtful that I’d get tighter control with a pump (current A1C is 5.9% with a high time in range). I think you need to know and understand the options available and then find what works for you.
Hi Christel-this was super helpful! I’ve had diabetes for almost 25 years and have never used a CGM (the technology wasn’t around when I first got a pump and just never got around to getting set up with one). The biggest hesitation for me is having the two sites going on at all times (I use the omnipod). You were mentioning your upper arm is best for you (thats where I put my omnipod) so wondering if you or anyone else here has experience balancing having the two injection sites? I already struggle to rotate my pod around and still feel like I can sleep and exercise comfortably with it on. Let me know! Any insight would be super helpful 🙂
I completely understand the hesitation related to multiple sites. I have friends who use Omnipod+CGM, so I’ve seen some with one on each arm, while other use other sites (lower back, abdominal, legs, etc.). I think you just have to be careful not to have the two sites too close to each other.
Although my upper arm is my preferred, I also use lower back, right above the belt. I do require a bit of flexibility to get it back there but is doable.
I’m currently using Dexcom with Omnipod and rotate the sites between right and left belly and arms, where I have some fat. Omnipod site changes every three days and the Dexcom site changes every seven which makes the rotation a bit complicated but not a bother. Rotation is important to minimize scar tissue and keep insulin absorption high.
Looking forward to the new Omnipod/Dexcom artificial pancreas next year.
I’ll add my voice to loving my CGM and the data it provides. Some worry about data overload, but I love being bg able to react more quickly to changes in my BG and you learn whay works better and what does not.
One note: Both the Animas Vibe and the Tandom pump integrate at least loosely with the Dexcom G4 CGM. The pumps don’t make changes – yet – but CGM data, but the information is available on the pump itself without the separate receiver. New versions of those pumps will further integrate, hopefully soon.
Hi Mark, thanks for the note. You are completely right on the integration, that was poorly worded and I’ll update it.
Glad to hear you also enjoy the data flow
Just found the blog and have enjoyed the first few articles that I’ve read. I’d be interested to get your thoughts on the CGM the second time around. I wore one for a few months a couple years ago but got frustrated and stopped when it was waking me up most nights. I know it would help my a1c but I think since I’m an avid runner I have nighttime fluctuations that cause it to go nuts.
Hi Josh,
I know what you mean, the alarms can be extremely annoying if you don’t need them. I fix that in two ways.
1. I’ve adjusted my Glucose Range setting from 12am-6am to be pretty broad (50-180)
2. If I know I’ll have fluctuations, but don’t expect to go severely high or low I’ll put it on silence
Of course, #2 only makes sense if you don’t need the readings real time. Like last week my sugars were weird (unexplainable morning highs), so I slapped on a sensor and it helped me identify a trend for when (around 1 am) my sugars started to creep up. So that information helped me fix it, but I didn’t need the info real time.
This week I have incorporated evening cardio which has made my sugars tank (took a total of 3.5 units bolus yesterday), so these nights I don’t have it on silence. I want it to wake me up if I’m about to crash.
Hope this answers your question – Christel
GREAT POST!!! THANK YOU for motivating those with diabetes to make fitness a priority! Being diagnosed is NOT a death sentence.