What does A1C measure and how often should it be checked?

• A. Average blood glucose over about 3 months; checked every 3 months after diagnosis or if not at goal, otherwise every 6 months.
• B. Average insulin level over 6 weeks; checked monthly.
• C. A single fasting glucose value.
• D. Blood pressure readings at every visit.

Answer: (A)

A1C shows how much glucose has been attached to hemoglobin over time, giving a picture of average blood glucose for about the past 2–3 months because red blood cells live roughly 120 days. It’s a measure of long-term glycemic control, not a snapshot of a single moment or a daily fluctuation. That’s why it’s used to monitor diabetes management and guide therapy changes.

Testing frequency is tied to how well blood sugar is controlled. After a new diagnosis or if glucose isn’t at goal, it’s checked every 3 months until control is achieved. Once at goal for at least 3 months, it’s checked every 6 months. Keep in mind that factors affecting red blood cells, like certain anemias or variants, can affect A1C accuracy, but in general this is the standard pattern for monitoring long-term glycemia.