Continuous Blood Glucose Monitoring - On-bike nutrition and its impact on blood sugar

[Trix8806]

@BCM

Worth mentioning - but I seem to remember that CGM’s aren’t accurate or reliable enough for measuring levels intra-exercise. Has to do with the fact they aren’t actually measuring blood glucose at all, they are measuring interstitial glucose which lags, and may not represent actual blood glucose intra-exercise.

This is interesting, and I could see it making sense in a way. I think the best way to determine this would be to spot check it with some finger pricks on a standard glucose monitor to compare.

And.. With that in mind.. I woke up this morning and my blood glucose was 113, which is concerning and in the pre-diabetic range. Never in my life have I been over 100? Maybe 101-103 a couple times, but it’s always been in the 80-95 range.

I checked the Dexcom box, and it looks like they have a short shelf life and my monitor is expired by about 8 months. A friend gave it to me around 15ish months ago, and I didn’t get around to using it right away. Between the 113 reading and expired date, I obviously became very concerned (and suspect). I pulled out my old regular blood glucose monitor, and checked it and it showed 77.. That would be great, except, those test strips were also significantly expired

SO! I just went to Walgreens and bought a new standard monitor and standard test strips. Just did a test and according to the finger prick, my blood glucose is 85 vs 121 on the Dexcom.

I am hoping (based on this mornings reading) that the expired Dexcom is no longer accurate. I will check the reading upon waking tomorrow morning vs a finger prick, and if it’s indeed off, I’m going to remove the Dexcom. Honestly, I hope it’s off vs having a fasting glucose at 113. I haven’t done an experiment like this since heavily implementing 100g carb of sugars into my training and had concerns it may have been throwing things off as a whole.

The good news is that I have another Dexcom G7 (that’s not expired) and once I get back from vacation I’ll restart this testing protocol.

I’m a certified quality auditor and the classroom work hounds on calibration/expirations an absurdly high amount. Obviously very important, but did seem like a little bit overkill in the training. I may be seeing first hand the importance of expiration/calibration. On an electronic assembly with an internal battery/monitor, I can see it’s importance more so than say.. a bottle of Tylenol.