My G6 "sensor failures" seem to be just my wild bg excursions

My G6 declared a sensor failure last night for for most of an hour, after my bg took a completely unexpected excursion into the stratosphere. But I cross-checked with a fingerstick and my bg really was taking that excursion.

A bit of background… sometimes I have been 90%+ TIR. Maybe not the “flatliner club” but really pretty good. But yesterday was an exception. I don’t know what the deal was yesterday I was zooming wildly low and high the whole day. But in every case a fingerstick test and my OneTouch Verio agreed with the G6.

I will admit that yesterday I tried moving my OTC Allergy pill to evening instead of afternoon and went out and mowed the grass late yesterday afternoon but I don’t know if that’s to blame for my huge wild excursions yesterday. Seems unlikely what time I take an allergy pill is responsible for multiple dips below 70 and an extended excursions above 300.

I have been using the G6 for 9 months now and in retrospect other hour-or-so sensor failures I’ve had it declare - AFTER the first 12 hours - were because of wild excursions in my bg that evidently my G6 didn’t believe but for which a cross-check with a fingerstick confirmed. I have been doing really well with 12-hour soak of new sensors before moving the transmitter to them.

Below is the curve from Clarity and I have highlighted the sensor offline area with my red text markup. Again yesterday was not a good day! Also note the hypo on the graph around midnight. That was real and also a PITA. I ate and ate and ate to bring that back up.

How high was your excursion when you finger checked it @Tim12 ?

My fingerstick meter (OneTouch Verio) said 350 but I know from past cross-checks on it that was probably 20 or 30 points on the high side.

Not that I have too many opportunities to calibrate my meters at that high end. I can think of a couple times in the past decades my meters just said “Hi”. I said hello back and at that point kinda wished I had my old visually read Chemstrips as a sanity check.

I had already delivered a correction bolus (see the glossary for “rage bolus” !) circa 6:30PM when the CGM passed 180 and beeped, and a fingerstick cross check showed me about 240. The rate of change was so high that the difference between 180 and 240 could’ve been largely just the 15 lag of a CGM.

I can kinda see why the G6 self-declares a sensor error when the rate of change seems crazy high, or the value is crazy high or low.

But if the rate of change is actually high or my bg is crazy high or low, that’s when the CGM is most useful.

So sort of a “heisenbug” case where the G6 declares itself untrustworthy exactly when I need the advantages of a CGM the most.

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I don’t know about the timing of a pill, but I do think allergies have a significant impact on blood sugar. I have at times quite severe allergies, and I think it definitely had a huge impact on my blood sugar.

Also, I find the weather has a big impact. I need more insulin during the fall and winter than I do in the spring and summer. So maybe the weather warming up (plus exercise from mowing the lawn plus allergen exposure if you’re allergic to grass) all contributed to the craziness.

Well the dexcom and all the sensors get used up.
If you sugars stay low then you use it up slowly. If you run high it goes faster.
So it makes sense that you could kill it with an extended high.