I had an odd experience with my CGM today, although the oddness was really in me.
I run after lunch every other day and normally reduce my lunchtime bolus a full unit to account for the run - generally 3 miles. As I walk to the gym to change it is not unusual for my CGM alarm to sound off indicating a high. It did that today, but when I looked at it it was actually alarming for a low.
I decided that it was full of crap. It had been ‘noisy’ all night. Stupidly I left my BG monitor at the office so couldn’t take a finger stick to confirm. In any case, I didn’t FEEL low. At least I didn’t THINK I did. The low alarm kept me wondering and I started to feel some minor tingling but the kind you get when you’re either high or low. I wondered if the CGM could induce a ‘psychosomatic low’?
Started the run - felt great - good form, nice pace, strong rhythm - wondering all the time, “am I going low or is the CGM full of it?” After a mile I felt it. It was me that was full of crap.
I ended the run, walked back to the gym, showered and changed, got to the office and did a finger stick. I was indeed low. Not as low as the CGM said, but too low to finish the run. At least I’d smartened up by then.
I finally figured out that the mid-morning correction bolus I’d taken earlier was probably the culprit - even though the bolus wizard should have accounted for it.
The lesson learned is to keep my BG monitor handy. There’s a reason not to fully trust the CGM for treatment decisions, it’s often off by 20 or more points - the source of my distrust. But since I have it I shouldn’t dismiss it. It was showing me a trend even if ti wasn’t right on the mark. With or without the BG monitor or CGM, it’s important to listen to your body.