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Dr. Bill's Commentaries

Time for CGM   (August 28, 2010)

Updated information about CGM may be found at What Is a Continuous Glucose Monitor (CGM)?

For the past two years, I've been using an insulin pump, and stabbing my fingertips for blood glucose samples multiple times daily. All the effort has paid off with normal A1C levels (they have ranged from 5.6 to 5.8 since I've been pumping).

With those A1Cs, both of my endocrinologists (the one where we previously lived in NJ, and my new endo at our new home in SC) have wondered whether I might also be having hypoglycemia unawareness: low glucose without warning symptoms. Of course, my obvious answer is "no" - but then, if I were low and unaware of being low, that's exactly the answer anyone would expect.

There is, of course, a foolproof way to find out if one is having low blood glucose levels: measure the level and find out if it's normal, high, or low. I do that between four and ten times most days, and occasionally see a low number, and promptly adjust my pump settings (using a "temporary rate" that's ¼ of the usual rate), and grab some carb. But how many lows might I be missing - especially at night when I'm not testing, or when traveling and preoccupied with the hassles of driving or flying?

The answer to this is CGM: continuous glucose monitoring. There are three brands: The SEVEN PLUS from DexCom, the FreeStyle Navigator by Abbott, and the Guardian REAL-Time System from Medtronic MiniMed. All three devices have "sensors" that are semipermanently stuck through the skin (and remain there for between 2 and 7 days before needing replacement). They also have components called transmitters and receivers, containing electronics and batteries and displays; one of the devices (from Medtronic) can communicate with an insulin pump (one made by Medtronic - duh), and another (DexCom's) device will soon be available to communicate with a different pump (from Animas/OneTouch). And all of the devices are expensive to buy, and replacement sensors are also expensive; although insurance will probably help with paying for the costs. There's a grid comparing the different CGM devices at the Children with Diabetes website, and another at

How to choose one of the three? Well, if you already have an insulin pump and are happy with it, you'll probably want to look at a CGM device that works with that pump. In my case, as I'm using an "orphan" pump (the Deltec Cozmo, which is no longer being sold), I could look at which pump I might switch to, or simply look at other features of the CGM device (or the preference if any of my endocrinologists). Both my endocrinologists favor one brand, and it's the one that happens to have a feature that's important to me: long sensor life. So I'll probably get a DexCom CGM soon. I'll keep you posted on how things work out.
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Dr. Bill Quick began writing at HealthCentral's diabetes website in November, 2006. These essays are reproduced at D-is-for-Diabetes with the permission of HealthCentral.

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This page was last updated at D-is-for-Diabetes on January 10, 2018

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