First Experience With CGM

As I’ve written about recently, I’m coming up on my 5 year anniversary of abandoning prescription medicine treatment of my Type 2 Diabetes by using the Paleo lifestyle and followers of this blog should have noticed that I’ve done that by using data to drive my decision making process.

And while I’ve tried on occasion to take frequent measurements per day to assess what impacts diet and exercise have on my blood glucose levels, there hasn’t been a way to monitor my blood glucose continually (i.e. every few minutes) and it’s just too much of a hassle to prick your finger dozens of times a day (and expensive!).

There have been continuous glucose monitors (CGM) out on the market for many years now but they have mainly been used to pair with insulin pumps and that really doesn’t help type 2 diabetics out who don’t need insulin injections.

But recently two new CGM devices have been approved by the FDA that don’t need to be paired with insulin pumps – Dexcom G5 and Abbott Freestyle Libre.

I recently got the Freestyle Libre and started using it yesterday and I’d like to share some of my initial findings.

What’s In The Box

First off the Freestyle Libre system involves two devices – a reader and a sensor.  The meter is a handheld device that looks very similar to a normal strip reader and while you can use Abbott strips to perform instant readings of blood glucose levels, the beauty of the CGM lies with the sensor.  The sensor is a disk that has a needle that inserts below the skin and this is how it takes glucose measurements every minute.

freestyle libre system pic 1

freestyle libre system pic 2.JPG

Inserting The Sensor

Each sensor can be used for up to 10 days and they come packaged individually with a special application device and alcohol wipes.  The sensor can only be installed on the back of the upper arm (where your triceps are) and I didn’t need help with this, as it was easy to do.  You pick up the sensor with the applicator and then push the applicator against the skin to ensure the needle and sensor properly attach to your arm (there is some sort of adhesive that makes sure the sensor is securely attached (more on the quality of this attachment later).

Full disclosure, I’m not a guy who likes needles and I’m quite the pansy in that regard and I’m not particularly proud of that.  With that being said, I will say that there was a brief amount of pain that lasted a few seconds when the sensor was applied and there was a dull ache/pain for about an hour but after that I forgot the sensor was there.

Obtaining Blood Glucose Data

After you insert the sensor you then activate it through the reader but for some reason, you have to wait 12 hours before you can take your first reading.  I don’t know if this 12-hour delay is only for the first sensor you apply or for each new one and I’ll find that out in about 10 days.

But after the 12-hour delay, you can download data from the sensor by turning on the reader and placing it about 1-2 inches from the sensor.  The reader beeps and then you see a graph of blood glucose levels for the past 8 hours.   You can add notes such as info on the meal you just ate and insulin injection by tapping the pencil icon, which takes you to other menus.

freestyle reader screen cap

Glucose Readings Compared To Stick Meter

I use the Livongo meter to take instantaneous glucose meters via the traditional finger prick/stick method and I compared blood glucose measurements (ug/dL) between the Livongo meter and the Freestyle CGM 4 times over the past 24 hours.

Livongo Freestyle Libre CGM
150 157
129 143
111 111
104 129

As you can see, the Freestyle Libre CGM was mostly higher than the Livongo meter with an average of +11.5 mg/dL.  Now it should be noted that the Livongo meter (like all glucose meters) have a larger margin of error than I’d like to see and I’m sure the Freestyle Libre CGM and Livongo are no different.  That is why I’ve always said to pay attention more to trends than the absolute values of individual measurements.  But this is something I’ll continue to watch to see if this delta continues or if the average goes to zero as the sample size gets larger.

I will say that I have good confidence in my Livongo meter because I’ve seen good correlation with my A1C measurements I get from my doctor’s office. During my visit last month I had an A1C reading of 6.0%, which corresponds, to a blood glucose level of 126 ug/dL and from my Livongo data, I’ve averaged 127 ug/dL for the last 90 days.

The Beauty Of CGM Data

OK, so that is the extent of my experience for the first 24 hours using this meter and expect many posts in the future as I dive into this new treasure trove of data but I couldn’t wait to analyze this data.

Since this was my first experience with a CGM I wanted to really put my body to the test by deviating from my Paleo diet and eating a couple meals of high carbs and follow that up with exercise to see how my body reacted.

For the past two days, prior to exercise, I have eaten a breakfast that consisted of 4 eggs and three pieces of ciabatta toast with butter and blackberry jelly.  Grains and jelly are basically verboten for me under Paleo but I have previously discovered that I can eat those prior to intense physical activity with no detrimental effects to my blood glucose levels. But that was when I measured my blood glucose levels after exercise and I had no idea what happened between the 2 hours after the meal and the end of my exercise.  Now with the CGM I can see what happens!

The two physical activities I planned were golf on 06-JUL-18 and riding my bike for 20 miles on 07-JUL-18. Golf is not nearly as strenuous as riding a bike for 20 miles so I mainly want to focus on 07-JUL-18 for right now.

As you can see from the screen cap from my Fitbit app, it took me about an hour and a half to ride 20 miles.  The manual for the Freestyle Libre states that the sensor is water proof up to 3 meters but swimming should be limited to 30 minutes.  During the bike ride, I was subjected to rain for the entire hour and a half of the ride and the sensor not only maintained its electrical functionality but stayed firmly attached even after the shower after the ride so the robustness of the sensor to water was validated.

bike ride fitbit 07-jul

I finished my breakfast on 07-JUL-18 around 10:30 and left on my bike ride at 11:05.  As you can see from the graph below, my blood glucose level peaked around 250 ug/dL at 11:20 but then came down to 97 when I finished my ride at 12:35.

daily log

It should also be noted that I had a dinner of pork, zucchini and mashed potatoes that caused my blood glucose levels to peak at 173 approximately an hour after the meal (potatoes are bad for me as they cause my blood sugar to spike more than if I ate something with a high content of sugar).

I should also add that the Freestyle Libre has an app/program that you can download to your computer to export the data to reports and the options available are shown in the pic below.

freestyle libre report options

So much more to come regarding my new CGM later but after the first 24 hours I’m extremely happy to have this new technology to help me control my type 2 diabetes!

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4 Responses to First Experience With CGM

  1. tannngl says:

    Interesting. I wondered how well it worked.
    As an aside, I have never had TTDM but have checked my blood sugars 1 and 2 hours after eating. They run around 99 to 105 but I eat ketogenicly.

    • cosmoscon says:

      Since you don’t have insulin sensitivity I’m not surprised your blood glucose levels are so low after a Keto meal. Even I, who does have insulin sensitivity, have blood glucose readings less than 115 after a Keto meal.

      I’ll have more data available on future posts as I get more data on this CGM!

  2. Pingback: Comparing Blood Glucose Measurements of Abbott Freestyle Libre vs. Livongo | cosmoscon

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