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HbA1c (A1C)

HbA1c, often called A1C, is a blood test that shows your average blood sugar over the last two to three months. Sugar sticks to a protein in red blood cells, and the test measures how much has stuck. Doctors use it to find and follow diabetes.

For experts

HbA1c measures the percentage of haemoglobin with glucose attached and so reflects average blood glucose over roughly the preceding three months, because glucose stays bound for the life of a red blood cell (about three months). It can be used to diagnose type 2 diabetes and prediabetes and is the primary test used in diabetes management.

Sources (2)

  1. 01Hemoglobin A1C (HbA1c) TestMedlinePlus, U.S. National Library of Medicine · 2025-05-20 · accessed 2026-09-29
  2. 02The A1C Test & DiabetesNational Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) · 2026-05-19 · accessed 2026-09-29