Dexcom G5 Inaccurate Readings after exercise and Showers

I switched from the Enlite and have been using the Dexcom G5 for about 2 months and it is more accurate most of the time than the Enlite. But I have noticed that it becomes very inaccurate during my 60 minute exercise and when I come out of a hot shower. During exercise, the sensor will drop drastically, like 50 to 100 points and slowly come back up to about where I started before beginning to exercise as soon as I stop. It does the same thing after a hot shower. I have started doing finger stick tests and discovered I really wasn’t falling and rising, like my sensor was telling me. Has anyone else experienced this? Am I doing something wrong? Is there something I can do to fix this? This is not only with the Dexcom, but it has happened to me with the Enlite as well. I want to rely on my CGM when exercising since the simptoms of a low, major sweating and racing heart are what you would normally feel during exercise.

I get the exact same thing…

CGM is a often inaccurate approximation of your blood sugar by reading interstitial fluid (glucose oxidase reaction with fluid to create hydrogen peroxide then reading something similar to “conductivity” in the H2O2 mixture), your BG meter is +/- 20% accurate and you use it to calibrate your CGM. The CGM really cannot, ever, be more accurate than your meter unless it’s by accident.

Things that contribute to more or less circulation at the skin, such as a hot shower or working out, can affect the interstitial fluid and so therefore the CGM reading. Things that interfere with the concentration of water at the interstitial fluid… if you are dehydrated for example, could interfere with the readings. Rapidly changing blood sugar will lead or lag the CGM reading because it takes time for the interstitial fluid to change and it is based on the difference in the sugar dissolved between the fluid and the blood.

Acetaminophen (Tylenol, and some over the counter cold medications), for a chemical example, is known for interfering with the reaction and the CGM readings.

the newest, best-of-all CGM is still pretty barbaric and inaccurate, but it beats the heck out of clini-test. At least you get good readings most of the time, which is in my opinion the best it’s going to be, for now. You are not doing anything wrong. good luck!