When the CGM refuses to update

Nice late night up continuously updating the CGM and it continues reverting back to the old (wrong) BG. Going on an hour now of changing it every 5 minutes because it refuses to accept/calibrate to the correct BG.

He had McDonalds right before bed last night and i figured it would cause highs. Before I went to bed at 11PM he was a cool 110 and i set my alarm for 2:15…woke up to find out reading HIGH (first time in a long while). So I came and did a fingerstick…275. High, but not 400+ high. Now I’ve spent the last 45 minutes doing 2 other fingerstick and confirming he’s coming down into the 250s and although i continue updating shortcut and doing triple calibrations on the CGM, it continues reverting back to “HIGH.”

It’s “one of those nights.”


Sorry for the long night and highs! :frowning: You probably already do this, but I learned here on FUD (from @daisymae) that calibration is more likely to take if you immediately enter one calibration right after the other. So two, 275s, for example.


I always do the shortcut which sends the BG to Apple Health and NS followed by triple calibration within the CGM app itself. That usually does the trick but didn’t last night.


Did you suspect the pump at all? And does Liam sleep through all the fingersticks? I hope you both got some rest today! :yawning_face: :sleeping:


I didn’t suspect the pump for the issue I had. The pump isn’t controlling or connecting to the CGM for purposes of the calibrations. He sometimes sleeps through the fingersticks but last night he woke up not happy after a stick…must have hit a sensitive spot.


There’s a shortcut that does that??? How does it work? I’m getting tired of calibrating my Dexcom again and again and having the Dex ignore my calibration.

I’m wasting lots of strips on this, and going to sleep knowing the Dexcom is wrong can be difficult for me.



Shortcuts won’t change the Dexcom’s stubborness, though. I have to repeatidly “triple calibrate” sometimes because Dexcom just believes “it knows best.”


@Ray and @ClaudnDaye I’ve never had my G6 refuse to accept a double calibration attempt, interesting that @ClaudnDaye has had this experience! I have had the experience of a single calibration resulting in about a mid-point change between the current G6 reading and the calibration reading (i.e. it says 100, I put in 150, it settles for ≈125), but if I calibrate a second time, it always gives way to my input number. That’s not to say on the next cycle it doesn’t adjust itself more to “it’s” liking. I’ve always figured it has to do with smoothing algorithm I understand is built in to the G6 (I haven’t verified it exists, just read a lot about it).


It’s hit or miss with me. Sometimes the calibrations result in what you experience…with meeting at some number in the middle between what the CGM reads and what his true BG is. Other times, we can go for an hour calibrating every 5, 10 or 15 minutes and it NEVER sticking. So, like…CGM may read “LOW” while he’s 110. Calibrating over and over and over and …you get the point, results in NO change. It just stays “LOW” until it feels like moving back up while reality was that he was NEVER low.


sorry to hear about the McDonald’s high, i know its too late and bad advice since he was sleeping, but i always found drinking lots and lots of water helps with the Dexcom persistent highs…maybe for the nexr McDonald’s high…

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It seems to have some TMI algorithm. I remember on the G4, before I abandoned Dexcom, that repeated calibration (more than twice a day) caused the software to abort and report a failed sensor. Since every sensor aborted I gave up (asked for my money back, never got it.)

So they got burned, perhaps by my insurance company too, and they stopped accepting too many calibrations; TMI.

With the G7 I simply don’t calibrate unless desperate. “Desperate” means that the erroneous readings coming out of the Dexcom are causing AAPS to deliver erroneous insulin to match. I only do it once or, once in a couple of months, twice in a day and I only do it if AAPS is going AWOL on the BS.

There’s too much built in to the Dexcom software for us to be able to correct or, as Dexcom would prefer to say, second guess it. It’s like everything else; trust it or use something else (Abbott is now an option). That’s “trust it” as in “understand what it can do and do not expect more”.


We use the G6. Hardly ever sensor errors now with calibrations (whether one or multiple) but very stubborn.

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Just bc i have found a calibration trick doesnt mean i dont experience this frokm tijme to time And, like you, I HATE wasting strips. It expensive and annoying and my fingers are terribly scared fro years of pricking. The tips are actually black and it difficult to find a site to get any blood out. :upside_down_face:


The best advice I’ve ever gotten, from my hcp was to not calibrate it at all—- or if you must, do it only one time for the entire life of the sensor, at least 24 hours after insertion.

Hard to do when it’s acting stupid but it significantly improved its overall performance for me

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Same for me.

Occasionally, with restart of same sensor, I will do 2 calibrations. First one with half the bg difference, then 5 minutes another BG test and enter second BG. But have only had to do this 2-3 times the past year, with large difference on restart.