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  • Writer's pictureEsther

Wearing a CGM

It´s the fourth time I am wearing a CGM - a Continuous Glucose Monitor - to track my glucose levels to learn a bit more about myself, my body`s reaction to food and activity, and my health.

As I am non-diabetic, tracking my glucose level is merely just for fun and to satisfy my curiosity. For others, however, tracking the glucose level is very important and especially for those with Level-1 diabetes to avoid hypoglycemia.

Non-diabetics, Level 1 and Level 2 diabetics

For non-diabetics, the glucose level is stabilizing itself. After a meal, the level goes up and as a reaction, the body produces insulin to put the sugar from the bloodstream into the cells. To avoid glucose levels falling too low the liver produces new glucose to be sent into the body to keep the level steady and in balance. This happens automatically and continuously. A non-diabetic doesn´t really spend a thought on this as it just works.

For type-1 diabetics, it is a bit differently, here the pancreas can´t produce enough insulin to lower the glucose levels, and the diabetic has to use external insulin to keep the balance. They have to do this every day in their life and need to be cautious to not "overdose" insulin as this leads to sugar levels too low that can be extremely dangerous.

The type-2 diabetics do or do not need external insulin to lower their blood sugar levels after a meal. While their pancreas produces enough insulin, the cells have gotten resistant to it and as a result, more insulin is needed to lower the glucose level.

While it has been communicated otherwise for years, type-2 diabetes is not a chronic disease and can be reverted by getting insulin sensitive again. A lifestyle change that focuses on low-carb and fasting can do the trick.


I am using the Abbott FreeStyle Libre 2 as CGM. It is not too expensive and easy to install, convenient, and painless.

I am not a fan of pricking myself in the finger and pressing blood out of my body. This old method is painful and outdated and on top of this, it only gives you the current value but not the developments and ups and downs. If you need to measure your blood sugar, my recommendation is: do all you can to get a CGM. Especially for people with type-1 diabetes, as the integrated alarms can help you to avoid low blood sugar levels and keeping your glucose levels in balance.


To use the CGM, I only need to download the FreeStyle App on my iPhone and "install" the CGM on my arm. Once applied, I scan my CGM with my phone via the NFC sensor. By the way: If done correctly, the application on the arm is completely painless. Only make sure to not attach it to your muscle.

After waiting for 60 minutes, the CGM is ready to be used for the next 14 days. During this time, it provides me with data about my blood sugar whenever I want to know it. Besides this, it even provides me much more information like my average glucose levels throughout the day, my HbA1c, the number of scans performed, the number of events with a low value, etc, etc. - massive data that provide heaps of insights.

The CGM has an internal memory chip that saves the data for 8 hours which results in the need to scan the CGM at least three times a day to get a full 24-hour insight of the data. Once you go over the 8 hours without a scan some data get lost. As I tend to sleep sometimes longer than 8 hours, I have a couple of blind spots in my graphs now and then. They drag the data from the end, which results in losing the data after the last scan before the eight-hour window started. With this, you always have the last 8 hours based on the most recent scan. Luckily there is no real upper limit and you can scan as much as you like 😎

I recommend using tape to secure the CGM against external influence, but this is optional. The glue that sticks to the skin is in normal cases good enough.

During my first experiment with a CGM, I was overly careful as I thought there is a solid needle in my arm that could hurt me if the CGM gets pressed into my arm when lying on it or something like this. After taking it off I realized how much of a fool I was: The "needle" is flexible and elastic and can´t hurt you at all.

Before I forget it: If you do not have a phone supporting NFC, you can use a reader provided by Abbott. Works nicely too.

Optimal glucose levels

When setting up the app, you can define your normal glucose range. If you´re a diabetic, your doctor will help you with this definition.

I defined my "green zone" between 70 and 110 mg/dL. That means, everything under 70 will be treated as too low and everything above as too high. Well - my goal is to eat and act to not leave this area too often independently from whether I wear a CGM or not.

Non-diabetics tend to have a level under 100 when not eating and after a meal, it normally goes not above 140 - and if - it goes under this value again quickly.

As I am -at least- trying to eat very low carb, my goal is to normally not exceed 110 even after meals. But as you can imagine: When wearing a CGM, the arena for self-experiments is opened up.

First results

I am kind of on the edge between a low level and a bit too-low when sticking to my normal diet which is carnivore-ish. Or I simply need to adjust my "normal" range to 60-110 to not get the app screaming at me in its alarming red color all the time.

The below image shows the value of the measurement (on top) and the development of my blood sugar during the last eight hours (below). The red color indicates the value is outside of my normal range.

The complete graph shown in this image can be defined as my fasting levels and I was sleeping most of the time. Actually, my last meal ended at 5:45 pm the day before. That means that this measurement took place at the 13-hour fasting mark.

Current glucose level and development of the last eight hours
Low glucose level

The below graph for the last 24 hours looks similar to the 8-hour graph above and tells me that my average glucose was at 72 mg/dL, which is actually pretty good IMHO. We see a relatively stable glucose level with some smaller self-corrections.

You can also see a small spike after my last meal at 5:45 pm. However my lunch is not visible at all, but no surprise: I was not eating any carbs that could have an influence on the glucose levels within my blood.

My findings and experiments

Being active increases my blood sugar

Let´s assume I am sitting on the couch with a blood sugar of 60. Standing up and going around will immediately push it to something around 80.

To proof this finding, I did a small test today: Once at work I walked on my treadmill at a slow pace but constantly to see how my body reacts. I did not break my fast and only drank water.

Here is the result: I think the below graph shows that my assumption is at least not fully absurd - I took a shower at 7:30 and got dressed to start work at 8 am and walked on the treadmill until 11:30. That means, that the moment I got more active, my blood sugar levels were increasing slightly. Whether this increase is significant to support my thesis is not clear, but we should also not forget that Adrenalin and Cortisol both push sugar into the blood. The overall levels remained in the low-normal ranges.

Let´s test carbs

Wearing a CGM magically makes me want to test my reactions to different foods. And so, I started a 2-day carb experiment filled with 3 carb-loaded meals.

My first carb-meal is a Thursday-night dinner with three bread rolls. For me, this is an unregular high carb load.

The next day, I am enjoying two more carb meals: Lunch and dinner.

And this is what happened: After my first dinner, my blood sugar began a multi-hour up-and-down phase between 145 and 55 mg/dL. During the night, I was waking up incredibly thirsty, and even during the next day, my blood sugar levels went above 100 even though I did not eat anything.

The apple in the below picture indicates the timing of my meals. The first meal was a low carb lunch, the second was the Thursday-night dinner with three bread rolls:

Let´s assume I ate between 150 - 200 g of carbs: This is still in normal ranges of eating carbs for most people. Some say staying below 150 g even counts as low carb - and I was maybe just slightly above that.

In the following picture, you can see my blood sugar on Friday (midnight to midnight) trying to get back into balance before noon (while fasting) but remaining volatile with ups above 100 and downs to as low as 55.

My next carb load for lunch was causing a glucose-peak followed by a quick falling of my blood sugar levels without the ups-and-downs I was facing after my first carb meal.

The second carb-dinner can be tracked easily by the vertical increase of my blood sugar level shortly after 6 pm.

There is a small phase of non-tracked blood sugar between 9 and 11 pm caused by the fact that I had a 10 hours break between my last measurement on Friday and my first on Saturday morning as the CGM itself can only save 8 hours.

Having a look at the following few hours on Saturday we see the blood sugar decreasing slowly back to the normal ranges but still in a rather high-normal area. Interestingly we no longer see dramatic corrections between too-high and too-low values beginning around midnight:

Can it be that the first carb meals caused the increased volatility as my body first needed to get used to the carbs and the higher insulin levels again? And can it be that once being "used" to it, the reaction of my body was more adjusted and softer?

Looking forward - my goal is to see what happens next when going back to low-low carb eating. How long will it take to get back to my former normal ranges between 60 and 90?

I will fast until today's dinner to get an approx. 24 hour fast. That should be enough to get rid of most of the carbs again.


Wearing a CGM and getting some insights into your inside is fascinating and an experiment worth repeating multiple times. There is so much to discover and based on the insights you gain, it´s easier to tweak your diet to find your sweet spot in which you strive. Personally, I think I feel best when being in the range between 60 and 80.

That does not mean I feel terrible when at 120, but this normally goes together with being stuffed with carbs and that makes me tired and thirsty and both is nothing I like to be. Also - my sleep has been worse after the two carb-loaded dinners and I definitely prefer having a calm and relaxed sleep than waking up from bad dreams being incredibly thirsty.

One thing for sure: This fourth time wearing a CGM is not my last time.

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