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Message: <blockquote data-quote="KennyA" data-source="post: 2763731" data-attributes="member: 517579">I'm wary of "averages" - the HbA1c counts the actual number of glycated red blood cells, and that number gives you an idea/estimate of where blood glucose levels have generally been over the last 2-3 months.  It isn't an average of anything.  I think most CGMs have a sort of "estimated HbA1c" function. However - CGMs are measuring glucose levels in interstitial fluid, and estimating a blood glucose vlaue from that. Then they're extrapolating from that estimate to a forecast HbA1c.They seem to vary a lot in accuracy, however, which I don't think is surprising. Last time I used a CGM (Libre) it was predicting an Hba1c that was significantly lower than actual HbA1c at the next test - if I remember correctly it was a 32 predicted against a 38 actual.  That's over 15% out. Given that these are normal BG levels and it didn't do too well on those, I did wonder if it might give better accuracy at higher BGs, and be calibrated to work  better in those levels. I did find this small study which used CGM results from non-diabetic people.  The blurb says that it was run mainly because CGM manufacturers didn't know what "normal" looked like for newer models. [URL unfurl="true"]https://pmc.ncbi.nlm.nih.gov/articles/PMC7296129/[/URL]</blockquote>

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