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Hemoglobin A1c, commonly known as HbA1c or glycated hemoglobin, is a blood test that measures the average blood sugar levels over the past two to three months. This test is essential for diagnosing diabetes and monitoring how well blood sugar is being controlled in people who already have the condition. Unlike regular blood glucose tests that show sugar levels at a single moment in time, the HbA1c test provides a broader picture of glucose control over an extended period.

The test works by measuring the percentage of hemoglobin proteins in red blood cells that have glucose attached to them. When sugar circulates in the bloodstream, it naturally binds to hemoglobin. Since red blood cells live for approximately three months, the HbA1c test reflects the average amount of glucose that has been present in the blood during that time frame. The higher the blood sugar levels have been, the more glucose will be attached to hemoglobin, resulting in a higher HbA1c percentage.

For most adults without diabetes, a normal HbA1c level is below 5.7 percent. Levels between 5.7 and 6.4 percent indicate prediabetes, which means blood sugar is higher than normal but not high enough to be classified as diabetes. An HbA1c level of 6.5 percent or higher on two separate tests indicates diabetes. For people already diagnosed with diabetes, the general treatment goal is usually to maintain HbA1c below 7 percent, though individual targets may vary based on age, health conditions, and other factors.

The HbA1c test offers several advantages over traditional glucose testing. It does not require fasting before the test, making it more convenient for patients. It is less affected by short-term fluctuations in blood sugar caused by stress, illness, or recent meals. Healthcare providers typically recommend this test at least twice a year for people with diabetes who are meeting treatment goals, and more frequently for those whose treatment has changed or who are not meeting their targets. The test is performed using a simple blood sample drawn from a vein, and results are usually available within a few days.