HbA1c is a blood test that measures the average level of glucose in a person's blood over the past two to three months. It is often used to diagnose and monitor diabetes, helping healthcare providers understand how well a person's blood sugar levels are being managed. The results of the HbA1c test are expressed as a percentage. A higher percentage indicates poorer blood sugar control, while a lower percentage suggests better management. Typically, an HbA1c level below 5.7% is considered normal, while levels of 6.5% or higher indicate diabetes.