Rock steady CGM, Freestyle meter all over: puzzled!

Dexcom sensor has been on for a couple of days, right on for 36 hours. The track is solid and steady all afternoon, towards the top of the range. No sports, no special activities.

Late afternoon, my son tests once, gets 213. He washes and dries his hands carefully, tests again, gets 215 (CGM still rock steady around 120). So he doses heavily with a pen (5 units), then tells me what happened and asks for my advice on calibrating: should he? I am puzzled. Meter problem? I tell him not to calibrate, and to test again in 10 minutes to see what happens, as I suspect a true peak going up and down very quickly, but not showing up on the CGM.

My son tests 15 minutes later: it is now 143. A few minutes later, it is back to within 5 of CGM, a CGM that is very steady around 120.

But now we have 5 units of insulin. No big deal, time for dinner anyway. We make dinner to match 4 units of insulin (using the extra unit to come back to the center of the range), and wait for the 45 minute mark when he should turn the corner. We wait, wait, wait. 40 minutes after he should have turned the corner (1 hour 25 minutes after injection) he starts going up a bit and we stack 4 more units. Five minutes later, he turns the corner :slight_smile:

Sometimes you really wonder what is going on! Do you have any thoughts on understanding this sequence?

Btw, when my son calibrated in the evening, the CGM was still right on.


The body is a wonderous place. Imagine all the stuff going on all the time in the body of someone with a functioning pancreas/immune system combo. It amazes me that someone without T1D can have such tight 5.5/6 A1C all the time…doing it manually one has to just scratch their heads and think…wow. Body is a magical place.


Not really sure, the 213 - 143 in 15 minutes seems really quick unless he IM’d it and did some exercises. Is that usual for you?

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The injected insulin could not do any of this. He went from 215 to 143 to 120 in about 30 minutes, before any insulin could become active (in fact, that insulin needed 85 minutes to become active instead of 45, another mystery possibly related). His hands were clean and dry.

And none of this meter BG activity was seen by the CGM.

What type of meter did he use? Was it the PDM meter?

If there is ever a question on one meter, it is useful to have a different meter to verify it against. If you have a bad meter or bad strips, doing 2 tests with it may not give you any better information, it could be 2 bad results. I would rather verify it against a different meter.

A drop from 215 to 120 in 30 minutes should be noticeable in how you feel. I would suspect that it was a bad meter result in this case.

Yes, it was the PDM meter. It is possible that it was a PDM meter issue. However, the meter worked well before and appears to work well now. The strips belong to a new box that we have been using for the past couple of days. The strips before the 213 reading and the strips after the 143 reading appear to work.

If he had an 80 point drop in 30 minutes, that’s pretty much a plummet. Would he feel something like that?

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We have seen super fast peaks that go up and down on their own in about 20 minutes, that you can see on the CGM, but normally they are smaller, 40 or 50. My son does not feel them.

This time, he felt something weird when he was high according to the PFDM meter, which is why he tested for no reason when he measured 213 and 215: his CGM was very steady around 120, but he felt something unusual. He could not even describe it.

He did not feel the drop though. I am guessing that, if it is not a meter artefact, he must has gone up like an elevator in the same time it took him to go down, and felt the high coming.

Such a strange series of events.

@Michel I’ve got no science behind this, but when I read your original post, all I could think was “he wasn’t at 213. Or maybe he wasn’t at 120.” But something was very strange.

Because I would agree with @Eric, an 80 point drop in minutes wouldn’t feel like fun from EH’s perspective. He’d notice and feel crappy I think - mostly due to the short duration.

Maybe @ClaudnDaye has it right - the body is complex and amazing!

How’d it work out? You mentioned he injected 4 additional units since he didn’t really turn the corner quickly. Did he wind up low?

That was my first reaction when he told me about being at 215. But, when I suggested testing a 3rd time, he told me he felt certain this were good measurements, because of his procedure, of the fact that he thought his hands had been clean the first time, and the fact that he cleaned and dried them thoroughly the second time. Whichever way we look at it something is strange.

I discussed this point with my son to understand what he feels. He says that he feels a drop like that when he has been high for a while, 45mn to an hour, but not if he goes up and down quickly. He says normally he does not feel it if he goes up quickly (unless he goes super high), but this time he did feel something weird which caused him to test.

Go figure. I don’t have a good answer, except for @ClaudnDaye’s thought!


@Michel, totally random thought here…but does he wear a fitness watch to track heart rate? I find that my heart rate can help me validate bg results. A fast bg drop for me elevates my heart rate…and a long term bg high elevates my heart rate.

@Michel I just took a nice hot shower. Bg was 90. It went up to 160 in the shower. Fifteen minutes later it’s 100 going down. No insulin or carbs involved.

Was a shower involved in your episode?


So interesting!

And Doc’s point about the shower makes sense too. Or maybe exercise. But I figured the exercise you’d have mentioned.

Really interesting about the heart rate @T1Allison!


That is really interesting! I tried to convince him to wear a smartwatch (@Chris says it works very well with his son) but he does not want one. I am wondering if he may be interested in a Fitbit or similar.

We get similar effects but not that high :slight_smile: But no, that was not a shower. He was just working at his desk all that time.


What reasons does he give? I have come to rely on mine more than ever I expected!

I think realistically insterstitial fluid only loosely correlates to what blood glucose is actually doing— so it’s not uncommon to get these unexplainable discrepancies. The situation you describe above is not unusual to my cgm experience.


Are you able to get good readings from a fitness watch?? I find that amazing. I’ve had to wear monitors for many years, and I’ve found that only a true monitor (like Polar) could give a reliable heart rate. FitBit showed crazy numbers, and when I went to look at reviews, it seemed those kind of results were very common. Even my Apple Watch— whatever it is called— is just no good for HR. Maybe it’s only a problem during exercise??


Fitbit seems great except during exercise, lol!


Like a sensor that’s really great except when you need your blood sugar… or a pump that’s perfect except for when you insulin…

Oh wait…

That’s what I’ve got. :smiley: