Which test is used to assess long-term glycemic control?

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

Answer: (C)

Long-term glycemic control is best assessed by looking at how much glucose has been attached to hemoglobin over time. HbA1c reflects the average blood glucose over the past two to three months because red blood cells carry hemoglobin for about that lifespan. Higher average glucose leads to more glucose sticking to hemoglobin, so the HbA1c percentage rises. This makes it a reliable gauge of chronic glycemia rather than a snapshot of a single moment.

Fasting plasma glucose, by contrast, shows glucose after an overnight fast and represents a short-term state. The oral glucose tolerance test measures how the body handles a glucose load, revealing how well glucose is cleared after a challenge, which is also more about immediate response. Random plasma glucose is a single measurement taken at an arbitrary time and can be affected by recent meals or illness. For capturing long-term glycemic control, HbA1c is the appropriate choice.