After using Dexcom on and off for a few years, now the G5, I found a flaw I wasn’t aware of before.  Often in the morning the sensor reads lowish (around 60) while my meter put me 30-ish points higher. For a long time I thought Dexcom just needed to be re-calibrated upon waking.

Then I recalled reading something someone had posted on Facebook called “compression lows.” I posted my own question on Facebook last week and got confirmation. If your sensor is on a place on your body – for me my upper left shoulder – and you sleep on it or roll on it while you sleep, the sensor begins to calculate lower blood sugars. 

While I sleep on my opposite side, before I go to sleep I read and I’m lying on the sensor to keep my book light from shining in my husband’s eyes. And, of course, we all roll in our sleep.

So, this morning, I ran this short, but irrefutable, experiment.

I woke up at 6:30 AM, checked on my meter which said 92 while my Dexcom said 90. Good start. Then I lay on on my arm where my sensor is; my sensor was now under the weight of my upper body. Presto – the next three numbers drop down on my Dexcom to 64 within 15 minutes (3 readings). I then rolled off the sensor, and sure enough the next four numbers take me right back up to 92.

I can’t believe Dexcom doesn’t talk about this. I searched the web and found nothing from the company, only reporting from other patient users. Thank god for that. There must be many users making inaccurate dosing decisions based on these false readings.

If you wear the sensor on your upper arm, how do you avoid this problem? And c’mon Dexcom tell it like it is. You know people are wearing it on various body sites, not exclusively the abdomen, the one place for which you submitted FDA approval.