Which laboratory value is used to monitor long-term glycemic control in diabetes?

• A. HbA1c
• B. Fasting plasma glucose
• C. Random plasma glucose
• D. Oral glucose tolerance test

Answer: (A)

Glycemic control over time is best assessed by HbA1c because glucose naturally attaches to hemoglobin in red blood cells, and since red cells live about 120 days, the HbA1c value reflects the average blood glucose over roughly the past 2 to 3 months. This makes it a reliable measure of long-term control in diabetes, not just a snapshot of a single moment. Fasting plasma glucose shows the level after an overnight fast, capturing a moment in time; random plasma glucose reflects glucose at a random moment (often influenced by recent meals); and the oral glucose tolerance test measures the body's response to a glucose load over a couple of hours, indicating how well glucose is handled in the short term. Because HbA1c smooths out daily fluctuations and provides a longer-term picture, it’s the best choice for monitoring sustained glycemic control.