A1C/Dexcom GMI accuracy

For the past several years my A1C has hovered around 6.5 to 6.8. Dexccom Clarity GMI has typically been within .1 to .3 of lab or finger stick results at Endo’s office, usually higher than the lab results. In June of this year a finger stick test at the Endo’s office gave a 6.0 result while, to the best of my recollection, my GMI showed 6.7 for 30 and 90 days. In Sept. a lab test showed my A1C to be 6.3 while my GMI showed 6.8 and 6.7 for 30 and 90 days. Why the sudden greater discrepancy between the A1C and GMI? I don’t believe my BS control has improved at all, certainly not to the 6.0 A1C! Which measurement is most accurate?

It’s so funny you bring this up. My last visit a mentioned it to my doctor. My reports and my Clarity reports were always in line. Ok, maybe off by .1 or .2. But this last time it was .7! And as usual, I was told those numbers are not out of line. And I said, yes, I understand the numbers are never going to be the same but ever since using the G6, they have been the same. So why now are they not matching like they use to?

Now I don’t worry that much any more about my A1C. I use my time in range for my thinking about making changes to my treatment plan. But the bummer is that lab work is in my file and all my doctors will be seeing that not my Clarity reports.

I was just wondering the same thing and asked about it. Not on the 90 day averages, i am just beginning to use the dexcom cgm, but the daily numbers are always different; the dexcom and the finger stick machine. The range differs from 20 to 40 points. And i am wondering why. Which one is accurate?

Finger stick A1C meters at Dr office may have a margin of error, based on how hydrated you are, compared to a lab draw.

But you can also try doing 2 fingersticks and bg check and get different numbers.

Even using same drop of blood on several meters will likely be different. How hydrated you are can impact too.

More important to watch A1C trend. Are you going up or down, and in your goal range.

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The last time I had a fingerstick A1c done in the office it was lower than I thought it would be. The nurse practitioner told me that they usually run lower than a lab test.

We need to understand that none of these methods are accurate enough to compare them to each other.

If you calibrate your dexcom against a finger stick machine you are calibrating an inaccurate result onto another inaccurate system.

When you use an in office a1c machine, they are 89% accurate.
Opposed to99.4% for the in laboratory test.

It is pointless to compare the numbers. They could be anything at any time.

I fairly trust my dexcom and unless it doesn’t match how i feel, I will trust it. I go by Time in range.

My laboratory A1c is almost always lower than my TIR suggests.
But then we have our own cycles and bodies to blame.
Red cells are produced mostly at night, so tight control at night skews your a1c lower, which is the case for me. But also if you allow yourself to go higher at night to combat lows, your a1c will appear higher than expected.

According to my ap. My a1 c should be 6.3% but it was 5.8% and that’s pretty much the same as it has always been since I started the G6.

Everyone has their own tolerance for it. If I’m under 6.5% I feel pretty happy. I also know that when I try to drive it down,I end up getting lows.

My goal is to have an a1c under 6 and I’ve been pretty successful over about 2 years.

I wouldn’t even bother with the in office a1c tests unless my doctor insisted