Hemoglobin A1c is a crucial test that measures the percentage of glycated hemoglobin in blood to evaluate long-term blood glucose control over the previous 2-3 months. This test is essential for diagnosing diabetes, identifying prediabetes, and monitoring glycemic control in diabetic patients. HbA1c reflects average blood glucose levels throughout the lifespan of red blood cells, providing a more stable indicator than daily glucose measurements. The test is particularly valuable for evaluating patients with suspected diabetes, monitoring treatment effectiveness, and guiding therapeutic decisions. HbA1c values help healthcare providers assess diabetes management and adjust treatment plans to achieve optimal glycemic control.