A Week With My New CGM

I’m slow to adopt new technology. I was the last among my group of friends to cave in and buy a cellphone. I tend to catch up to whatever social media platform is popular just in time for it become utterly obsolete. I’m a musician, and my primary instrument is the Hammond organ, a beautiful beast of an instrument that stopped production in the mid-70s. (They’ve since started back up, building digital replicas of their old flagship electromechanical masterpieces, but even these digital machines are using all that computing power to replicate a sound generated by an electromechanical process created around 1930).

So it should come as no surprise that I’ve had a continuous glucose monitor (CGM) sitting unused in my house for the last nine months. I got it at the suggestion of my endocrinologist, opened it up, looked at the manual, got overwhelmed, and shelved it. And there it sat, unused, until yesterday. I don’t know what magic in the universe finally convinced me to set the thing up and get started, but I did. And it has already changed my life. Over the next few weeks, I’m going to tell you all about it, in case there are others out there like me.

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What it IS…and what it isn’t
First of all, let’s go through exactly what a CGM is, and how it works. A CGM measures sugar every five minutes, using a sensor that is attached to the user with adhesive. The sensor has a very thin, flexible probe that goes under the skin (very similar to the infusion set on an insulin pump). In my case, the sensor can be worn for seven days, and then should be changed. Other CGMs have varying sensor lives, ranging from three to seven days. The sensor has a wireless transmitter attached that sends the readings to the receiver, the brains of the system. The receiver is usually about the size of a cellphone (again, similar in size to many pumps), and provides a graphical view of the blood sugar readings. You can also input activities, insulin dosages, carbohydrates, and exercise in the receiver unit. My unit even has an option to relay the information via Bluetooth to an app on my iPhone. Last night, I was playing music on stage, and instead of having to guess what my number might be, or stop playing and stick my finger, I was able to glance briefly down at my phone, where my sugar level was displayed on the screen! Very, very cool!

Having this constant stream of information is incredibly useful, and it might sound like finger sticks would be a thing of the past — oh, that this were true! The information IS very useful, and in its first 24 hours, my monitor has been pretty accurate. However, CGMs still require calibration with finger stick readings at least once every 12 hours. This means taking a conventional blood sugar reading, and then inputting the number into the receiver. The receiver then calculates the difference in what you input with what it’s reading to get a more accurate number. Why do we need to do this? We do this because a CGM isn’t measuring glucose in your blood, but rather the glucose in your interstitial fluid (fluid between the cells). The glucose in this interstitial fluid lags behind the glucose in your blood by about 10–15 minutes. Because of this, CGMs need to be paired with traditional finger stick readings, and insulin dosing should still be based on those traditional meter readings.

My experience — day 1
I will continue this blog series for a few weeks, relaying my day-to-day experience as I explore this new device. But already after the first day, I have seen patterns more clearly than I EVER did with finger sticks alone. I have lowered my long-acting dose after seeing a crystal clear pattern of sagging numbers all day yesterday. What I realized is that with this device, I don’t have to be constantly checking my blood sugar at JUST THE RIGHT TIMES to catch a pattern. I can let it work in the background while I teach music lessons, or play music on stage (two areas where it can be hard to find those spare minutes to do a traditional glucose test), and then look back over the graph and see EXACTLY how and when my sugars rose or fell. I can see how sharply they rose, how sharply they fell, and what that means for my insulin. As I said, yesterday showed VERY clearly that my daytime long-acting dose is too high. As I went through my day, I would see a slow fall, then drink a little juice, see a bump up, followed by another slow fall, until I drank more juice, followed by a bump up, then ANOTHER slow fall. And I could do all this by simply glancing at my phone, which meant I could be tracking all this in the middle of teaching a lesson with no odd disruption for my students!

That’s all for this week. Tune in next week for more!