Which test is used to assess average blood glucose over the past 2-3 months by analyzing a modified form of hemoglobin?

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

Answer: (B)

The test being described measures long-term blood glucose by looking at a modified form of hemoglobin. Glucose slowly attaches to hemoglobin in red blood cells over their lifespan, which is about 120 days. The result, HbA1c, is the percentage of hemoglobin that has become glycated, so it reflects the average blood glucose concentration over roughly the past two to three months. Higher average glucose leads to a higher HbA1c, making it a useful gauge of long-term glycemic control.

In contrast, a random glucose test measures glucose at a single moment and doesn’t reflect past levels. Fasting plasma glucose assesses glucose after an overnight fast, not the overall average. The glucose tolerance test evaluates how well the body handles a glucose load over a few hours, providing information about glucose tolerance rather than long-term control.