Which test measures the body's ability to control blood glucose levels?

The Hemoglobin A1c test is a crucial tool for measuring how well the body controls blood glucose levels over time. It assesses the average level of blood sugar (glucose) attached to hemoglobin in red blood cells over a period of approximately two to three months. This test is particularly significant for diagnosing and monitoring diabetes because it reflects long-term glucose management rather than fluctuations that might occur throughout a single day.

In contrast, a Complete Blood Count provides insights into various blood components, such as red and white blood cells and platelets, but does not specifically evaluate glucose levels. The Prothrombin time test is used primarily to assess blood clotting and the effectiveness of anticoagulant medications, while the Blood urea nitrogen test measures kidney function and does not relate to glucose control. Thus, the Hemoglobin A1c test is the most relevant measure of the body's ability to manage blood glucose levels over time.