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Hemoglobin A1c, commonly known as HbA1c or glycated hemoglobin, is a crucial blood 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. Because 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 informative than daily glucose measurements which only show blood sugar at a single point in time.

The test works by measuring how much glucose has bonded to hemoglobin in the bloodstream. When blood sugar levels are consistently high, more glucose attaches to hemoglobin molecules. This process is called glycation. Unlike regular blood glucose tests that require fasting, the HbA1c test can be performed at any time of day and does not require any special preparation, making it convenient for patients. The result is expressed as a percentage, indicating what proportion of hemoglobin has glucose attached to it.

For people without diabetes, a normal HbA1c level is typically below 5.7 percent. Values between 5.7 and 6.4 percent indicate prediabetes, a condition where 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 individuals already diagnosed with diabetes, the general treatment goal is to maintain HbA1c below 7 percent, though target levels may vary based on individual circumstances, age, and other health conditions.

Healthcare providers recommend HbA1c testing at least twice a year for people with diabetes who are meeting treatment goals and have stable blood sugar control. Those who have changed their treatment plan or are not meeting their targets may need testing more frequently, typically every three months. Regular monitoring helps healthcare providers adjust treatment plans and helps patients understand how well their diabetes management strategies are working. The test is also valuable for assessing the risk of developing diabetes-related complications, as higher HbA1c levels are associated with increased risk of damage to eyes, kidneys, nerves, and blood vessels over time.