A1C (Hemoglobin A1C)
Also called: HbA1c, glycated hemoglobin
A blood test that shows your average blood sugar over the last 3 months.
A1C measures how much sugar (glucose) is attached to your red blood cells. Because red blood cells live about 3 months, A1C reflects your average blood sugar over that window — not just the day of the test. An A1C of 5.7-6.4% is prediabetes; 6.5% or higher is diabetes.
Medically reviewed by Dr. Ikechukwu Ogbu, MD
MD · Board-Certified, Internal Medicine · Last reviewed June 2026