Morning CGM Phenom

Back to using Dexcom after 6 months’ sojourn with MedT Guardian 3, and here’s a thing that seems to be a persistent issue for me across both platforms: they both register too low during the dawn phenom hours. Interestingly, they do it differently: the Guardians would track low when the phenom first starts kicking in in the hour or two before I wake up, which was a real problem when I was using the 670 auto mode. The Dexcoms on the other hand are mostly dead-on when I do my a.m. fasting finger stick, but continue to tell me I’m doing great when my BG continues to rise over the next few hours, which means I always have to do a finger stick and, frequently, a calibration around 10:30 to get it back on track by the time of my mid-day meal.

Not sure if the causation is the same for both systems, but it is a PITA, and consistent enough that I really wish I had some kind of fix for it. One thing I’ve noticed about the Dexcom over the 4-5 years I’ve been using them is that they really tend to go a bit whacky when I take my morning shower. Always in the low direction, too, sometimes quite dramatically. FWIW I’ve used various insertion sites, mostly preferring back of the upper arm, but the phenomenon seems to be independent of location. Anyone else experience this, and have you found a reason or a fix? I’ve tried Dexcom support but they just run through all the standard questions and don’t seem to have anything useful to suggest.

No comments on the Gaurdian, but I know with the G5, if I don’t stay hydrated enough, it is slower to catch up on numbers changing.
So I drink a glass of water when I get up, and this helps me out.
Matter of fact, this has been the single biggest thing for making Dexcom work better for me. Drinking more water and staying well hydrated.


Good advice, but in my case, I already do that too. Hmph.

I’m afraid I don’t have a fix, but I’ve experienced the same thing with Dexcom. After breakfast, my BG sometimes goes up a lot but the Dexcom doesn’t keep up with it and shows a much lower number. I’ve sometimes felt that doing a corrective calibration when it’s still rising and the numbers are far apart makes the overall accuracy worse and that it’s better to enter a calibration a bit later when the Dexcom has mostly caught up with my BG, but I haven’t really tested that. It’s more of an impression.

No helpful advice ,but I’ll throw a monkey wrench into the mix…

My Dexcom used to always show numbers that were significantly lower than my meter in the morning or shortly thereafter; however, lately that trend has REVERSED – now, my Dexcom is likely to show 20-40pts higher than my meter upon rising - usually showing no signs of self-correcting until I calibrate it. I do hydrate early, and agree that that can impact it, but this problem seems to happen regardless of hydration.

Yah. “Did you have anything containing acetaminophen…?” :stuck_out_tongue_winking_eye:

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They’re gonna have to give that one up when the G6 pries it from their cold dead hands.

I can’t back this up empirically but it definitely seems like taking a shower sometimes triggers it. Frequently I see a drop right after I finish showering, not enough to get a down arrow but this morning, for example, it went down rather speedily into the 90s (I wish!) while I was finishing ma toilette, when by finger stick it was more like 120. I’ve actually asked Dexcom about this, because it makes sense–immersion in warm water is known to have vascular effects. But they would neither confirm nor deny. If it is the/a cause, I can’t think what to do about it. Cold showers? Not gonna happen.

My Dexcom is notoriously 20 points higher in the morning when I wake up. If Dex says 89, I am probably 69 on my meter. What is worse is if the Dex is 69, then my meter might be in the low 50’s. Through most of the day Dexcom tends to cry wolf with my lows and is often lower than my meter. Therefore I can’t calibrate with my wake-up numbers because then Dex reads even lower through the day. Usually through the night my meter and Dex are in sync and I am not quite sure what time they deviate. But after I’ve been up a while, the meter moves up and the Dex moves down and they’re in the ballpark.

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I seem to have the same issues with my Dexcom. I’m good when I wake up, but after my shower, frequently my Dexcom reads lower than my meter. Not all the time but often enough to notice. I’ve gotten to where I time my calibration for 30-45 minutes after my shower. That seems to get things back on track for me.