Glycated hemoglobin (HbA1c) is the product of the binding between hemoglobin and glucose in the blood. Hemoglobin is the protein inside red blood cells that transports oxygen. When glucose in the blood comes into contact with hemoglobin, they bind slowly and irreversibly to form HbA1c.
HbA1c reflects the average blood glucose level over the past 2–3 months and is a key indicator for evaluating the long‑term control of diabetes.
HbA1c Reference Ranges
Normal: < 5.7%
Prediabetes: 5.7–6.4%
Diabetes diagnosis: ≥ 6.5%
However, diagnosing diabetes using HbA1c has limitations:
It does not reflect short‑term fluctuations: cannot detect hypoglycemic episodes or postprandial hyperglycemia.
Affected by medical conditions: anemia, hemoglobin variants (such as thalassemia), renal failure, etc., may cause inaccurate results.
Individual variations: target values need personalized adjustment for the elderly, children, and pregnant women.