Why A1c can be different from eA1c and GMI

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My numbers were very similar…and my a1c came in at 6.7!! Go figure?!

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@Chris. Actually, someone has. PGS, or Patient Glycemic Score, is a measure of the glucose variability index, time in range, and measures of hypoglycemia both below 70 and below 55, over a specific time period.

It is a difficult computation but there are some apps that do it for you, xDrip+ being one of them. When taken with the GVI (Glucose Variability Index) it is easy to gauge both the altitude and amplitude of a track.

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Silly question… Can/will anyone please elaborate on the iron deficiency comments referred to above? I have pernicious anemia. For most of my life…but I don’t comprehend the diabetes part of the relationship. Maybe I shouldn’t have skipped biology in 8th grade or something, but I have never read or heard of a correlation between the two before.

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I’m not entirely sure if there’s a direct connection between the two, but studies have shown that your A1c may be higher or lower than you would expect (based on studies showing a positive linear correlation between A1c and mean glucose) because of anemia. I’ll paste a few studies below, but I haven’t read through all of them. Most conclude that iron-deficiency anemia results in a falsely elevated A1c and hemolytic anemia results in a falsely lowered A1c. I came across this possibility while wondering why my predicted A1c (based on average bg level) and actual A1c were pretty far off.



I don’t know a lot about pernicious anemia, but I think that means that you can’t digest B12 properly. I’d guess that you get B12 shots? Please correct me if I’m wrong.

A few years ago, I had insufficient B12 levels by US standards (deficient according to a few other countries) and deficient Vitamin D levels (by all standards) . It took my doctor time to figure it out, and my quality of life was significantly affected. It was like I was in a fog all the time. There were lots of issues going on. My eyesight was affected during this time frame too, but I can’t prove that it was a result of the vitamin problems and it did not get better once my levels normalized.

The fog and the other symptoms mostly left once my vitamin levels normalized by taking supplements. I’ve had my B12 levels tested since then, and they’ve been normal so I don’t think I had pernicious anemia. I wasn’t vegetarian, so there’s no reason I should’ve had a B12 problem though. The research article below indicates there’s a relationship between B12 deficiency and diabetes.

Here’s an article about the relationship between diabetes and pernicious anemia:

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@Katers87 Thank you very much for the articles. Looks like I have some reading to do. My B levels have been sub threshold since I was in knickers. I take sub-lingual b 2x daily, and it’s still low. The vitamin D thing though I have a handle on thx to the weather in California.

I appreciate the articles very much!

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I couldn’t revisiting this thread full of interesting data and sources after the recent discussion we had on GMI vs A1c:

I’m late to the party here, but I think that the theory behind the relationship with anemia and A1c kinda goes as:

Anemia=low numbers of RBC
A1c=measurement of glycation of RBC (by proportion of RBC)

Glucose within serum will bind to hemoglobin on RBCs, and A1c is our way of measuring that. If you have two individuals with the same blood glucose levels, but one is anemic, then the anemic individual has less RBCs for glucose to bind to. The absolute number of RBCs could be the same within the two individuals, but there’s just less RBCs overall in the anemic individual. So the proportion of glycated RBCs/total RBCs (A1c) will be higher in the anemic individual because of a reduction in the total amount of RBCs.

This does not consider the lifespans of RBCs though

Also, if I’m off, then someone feel free to correct me!

If you are referring to iron-deficiency anemia, yes it can cause an increase in A1C.

Your theory is reasonable, but the reason that an iron-deficiency anemia can increase A1C is not fully understood. Some believe it has to do with oxidative stress. Others believe that with iron-deficiency anemia, since the production of RBC’s is reduced, the RBC’s will last longer, and will ultimately lead to higher A1C numbers.

Unfortunately, there is no cheap, easy, and accurate way of determining RBC lifespan. You can do a reticulocyte count, but that is just an estimate. You could do a reticulocyte staining procedure, (REBEL - Reticulocyte Based Estimation of Red Blood Cell Lifespan), but that’s not something insurance would likely cover.

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How about if someone has Thalassemia, an inherited blood disorder where red blood cells are smaller than normal and can cause severe anemia? Would that also cause an a1c discrepancy - increase or decrease?

Thalassemia shortens RBC lifespan, so it would reduce A1C.

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Ah, thank you! Maybe that is why I can achieve an a1c of 4.9 :frowning:

Confusing because my lab a1c is consistently higher by 0.3 than my a1c as calculated by xDrip+ / Dexcom which just uses the CGM BG avg values, not the actual glycosylated hemoglobin as in the lab test:

“A1c:” + (Math.round(10 * (avg + 46.7) / 28.7) / 10d) + “%”;

I think the CGM estimates are not very reliable for many people.

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True, that is the case for me for some percentage of the time, for sure. :frowning:

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I am sure the numbers would not change significantly. If you are achieving a 4.9 with RBC’s that live only 10 weeks, it would certainly not jump up to anything horrible if they lived 15 weeks. The 4.9 is a reflection of your good control.

Also, since you run a lot, your hematocrit and hemoglobin may be lower than normal, because running has increased your blood plasma volume.

Don’t worry too much if you see lower numbers there. I think you are in great shape. Keep doing what you are doing.

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Yes, they usually are, too!

Thank you, I appreciate this!! :sunny:

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Google “Runner’s Anemia”. Take it as a sign that you are kickin’ it.

Also, check out your blood counts and your A1C after a hard training period, about 10-14 days after a race. See how it drops. That is a badge of honor. Wear it proudly.

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Oh, wow, I hadn’t heard of that before. Next endo appt is April but hope to have annual physical in Mar! I’ll aim for that time frame to see how the CBC looks!

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I found this googling Runner’s Anemia …

One effect of regular endurance exercise is that it produces an increase in red blood cell mass and plasma volume

I didn’t realize this… No wonder I feel so much better w/ nice, long runs.

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I think one of the other effects of thalassemia is that your body will counter the misshaped RBC’s by creating more of them.

As discussed earlier in this thread, possibly this could lower A1C, at least in theory.

Have you been checked for thalassemia?

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Yes, I learned I had it when I was young. Initially thought to be just anemia but further tests showed it was thalassemia minor.

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