Which laboratory value is used to monitor glycemic control over the past 2-3 months in diabetes?

Which laboratory value is used to monitor glycemic control over the past 2-3 months in diabetes?

• A. Fasting plasma glucose
• B. Random plasma glucose
• C. Hemoglobin A1c
• D. Oral glucose tolerance test

Answer: (C)

Long-term glycemic control is best assessed by a measure that reflects average glucose over months. Hemoglobin A1c does this because glucose gradually attaches to circulating hemoglobin, and the amount of glycated hemoglobin rises with higher average glucose. Red blood cells live about 120 days, so the A1c level mirrors the average blood glucose over roughly the past 2–3 months. It isn’t driven by a single meal or short-term fluctuations and doesn’t require fasting, making it ideal for monitoring ongoing control. The other tests capture more immediate glucose status or diagnostic responses: fasting plasma glucose shows a single fasting reading, random plasma glucose captures glucose at a random time without considering long-term trends, and the oral glucose tolerance test measures the body’s response to a glucose load over a couple of hours and is primarily used for diagnosis rather than ongoing control.

Long-term glycemic control is best assessed by a measure that reflects average glucose over months. Hemoglobin A1c does this because glucose gradually attaches to circulating hemoglobin, and the amount of glycated hemoglobin rises with higher average glucose. Red blood cells live about 120 days, so the A1c level mirrors the average blood glucose over roughly the past 2–3 months. It isn’t driven by a single meal or short-term fluctuations and doesn’t require fasting, making it ideal for monitoring ongoing control.

The other tests capture more immediate glucose status or diagnostic responses: fasting plasma glucose shows a single fasting reading, random plasma glucose captures glucose at a random time without considering long-term trends, and the oral glucose tolerance test measures the body’s response to a glucose load over a couple of hours and is primarily used for diagnosis rather than ongoing control.