The Glycated Hemoglobin A1c (HbA1c) test measures the average blood glucose levels over the past 2-3 months. It assesses the percentage of hemoglobin (a protein in red blood cells) that is coated with sugar (glycated). This test is widely used to diagnose and monitor diabetes by determining long-term blood sugar control. Higher HbA1c levels suggest poor glucose management, which may indicate a risk for complications in diabetic patients.