Which laboratory test is used to evaluate long-term glycemic control?

The laboratory test used to evaluate long-term glycemic control is glycosylated hemoglobin, commonly referred to as HbA1c. This test measures the average blood glucose levels over the past two to three months by determining the percentage of hemoglobin that is glycated, or coated with sugar. It provides a broader picture of how well an individual’s blood sugar has been managed over time, which is crucial for the management of diabetes and assessing overall glycemic control.

In contrast, tests like fasting blood glucose and random blood glucose provide a snapshot of glucose levels at a single point in time, which does not reflect long-term trends. The oral glucose tolerance test assesses the body's response to a glucose load but also does not give an indication of average glucose levels over an extended period. Therefore, glycosylated hemoglobin is the most reliable test for understanding long-term glycemic control and managing diabetes effectively.