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HbA1c

The percentage of hemoglobin that is glycated (bound to glucose), reflecting average blood glucose over the past 2-3 months — the lifespan of red blood cells.
Also known as:
Blood Hemoglobin A1cB-HbA1c.

HbA1c ranges

Interpret your result
"Normal" lab range for HbA1c is between 4.8 and 5.6%:
4.8
5.6
According to Peter Attia, HbA1c should be below 5.7%:
5.7
According to OptimalDX, HbA1c should be between 4.6 and 5.3%:
4.6
5.3
According to ADA, HbA1c should be below 6.5%:
5.7
6.5
Optimal range
Optimal range for HbA1c appears to be between 4.6 and 5.3%:
4.3
4.6
5.3
5.7
Prediabetes
6.5
Diabetes
10
Why this optimal range?
Preliminary range is based on functional health organizations including but not limited to those listed above.

What a low value may mean:

Common reasons for low HbA1c:

  • Low HbA1c can reflect genuinely low average glucose — recurrent hypoglycemia or severe caloric restriction.

    More often it is falsely low from a shortened red blood cell lifespan or faster turnover: hemolytic anemia, recent blood loss, donation, or transfusion, advanced liver disease, pregnancy, and some hemoglobin variants (sickle cell, thalassemia).

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What a high value may mean:

Common reasons for high HbA1c:

  • High HbA1c usually reflects sustained hyperglycemia — prediabetes, type 2 diabetes, insulin resistance, and metabolic syndrome. It also rises with obesity, glucocorticoid use, and smoking.

    It can be falsely elevated when red blood cells live longer or turn over slowly: iron, B12, or folate deficiency anemia, asplenia, chronic kidney disease, and certain hemoglobin variants.

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Zsolt Szabo
Zsolt Szabo
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I am particularly interested in research on biomarkers associated with all-cause mortality and on defining optimal reference ranges.