CGM Variation with exercise

I'm started the P90x program after a little too much of the good life. I have been successfully wearing the Dexcom unit in my upper arms until a couple days ago. It seems that with the amount of heavy exercise I am doing the Dexcom readings become quite varied.

An hour after exercise I had a reading of 187 on the CGM compared to a 97 via the finger stick. I saw this variation throughout the day, so I can't contribute it to a fast falling BG due to exercise.

Anyone else experience this?

My experience with the Dexcom and exercise is that the Dexcom becomes unreliable with intense physical activity. I have no idea why this would be, but it’s been my experience. I always wear the transmitter on my abdomen and I’m a runner, so I don’t think it’s related to use of the muscles near the insertion site. It may be that BS levels are changing too fast for the Dex to keep up.

How long after exercising did it take for the Dex to ‘calm down’?


It seemed to be within an hour and I had some funky readings the following morning. After an instense cardio workout today it’s playing nice and tracking my BGs well.

I had recently placed the set so I’m wondering if it was due to a nice site location combined with the exercise.

As glucose is ‘mobilized’ for use in muscles, it can cause a rise in the BG reported via interstitial fluid but NOT really be apparent in your BG.

So not really a problem, but definitely annoying!