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Hemoglobin A1c, commonly known as HbA1c or glycated hemoglobin, is a crucial laboratory test used to monitor long-term blood sugar control in people with diabetes and to diagnose the condition. 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 sugar levels over the past two to three months, making it more comprehensive than daily blood glucose measurements that only show values at specific moments.

The test works by measuring how much glucose has bonded to hemoglobin in the bloodstream. When blood sugar levels are consistently elevated, more glucose attaches to hemoglobin molecules. Unlike regular blood glucose tests, the HbA1c test does not require fasting and can be performed at any time of day, making it convenient for patients. The result is expressed as a percentage, with higher percentages indicating poorer blood sugar control and greater risk of diabetes-related complications.

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 American Diabetes Association generally recommends maintaining HbA1c levels below 7 percent to reduce the risk of complications, though individual targets may vary based on age, overall health, and other factors.

Healthcare providers typically recommend HbA1c testing at least twice a year for diabetic patients who are meeting treatment goals and have stable blood sugar control. For those whose treatment has changed or who are not meeting their targets, testing may be recommended every three months. The test is valuable because it helps doctors and patients assess whether diabetes management strategies, including medication, diet, and exercise, are working effectively over time. Regular monitoring through HbA1c testing enables timely adjustments to treatment plans and helps prevent serious complications such as heart disease, kidney damage, nerve problems, and vision loss associated with poorly controlled diabetes.