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Hemoglobin A1c, commonly known as HbA1c or glycated hemoglobin, is a crucial blood test used to monitor blood sugar control over time. This test measures the percentage of hemoglobin proteins in red blood cells that have glucose attached to them. Since red blood cells live for approximately three months, the HbA1c test provides an average picture of blood glucose levels over the past two to three months. This makes it particularly valuable for diagnosing diabetes and monitoring how well diabetes is being managed.

The test works by measuring the amount of glucose that has bonded with hemoglobin in the blood. When blood sugar levels are consistently high, more glucose attaches to hemoglobin molecules. This process is called glycation. Unlike daily blood glucose tests that show sugar levels at a single point in time, HbA1c reflects long-term glucose control, making it less affected by short-term fluctuations caused by recent meals, exercise, or stress.

For diagnostic purposes, an HbA1c level below 5.7 percent is considered normal. A result between 5.7 and 6.4 percent indicates prediabetes, which means blood sugar levels are higher than normal but not yet 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 to maintain HbA1c below 7 percent, though individual targets may vary based on age, overall health, and other factors.

The HbA1c test offers several advantages over traditional glucose testing. It does not require fasting, can be done at any time of day, and is not affected by temporary stress or illness. However, certain conditions can affect the accuracy of results, including anemia, recent blood loss, certain hemoglobin variants, kidney disease, and liver disease. Regular HbA1c testing, typically every three to six months for people with diabetes, helps healthcare providers adjust treatment plans and helps patients understand how lifestyle choices affect their long-term blood sugar control.