Glycated Hemoglobin (HbA1c) Test

The glycated hemoglobin (HbA1c) test measures the percentage of hemoglobin bound to glucose in red blood cells. When blood sugar (glucose) levels rise, hemoglobin irreversibly binds to the hemoglobin within red blood cells. Because red blood cells have a lifespan of approximately 120 days (3-4 months), this test result reflects average blood sugar levels over that period, providing a more stable and less volatile indicator than random or fasting blood glucose tests.