HbA1c test: your average blood sugar over three months

By Dr B.C. Gupta, MD · 2026-08-15

An HbA1c test measures your average blood sugar level over the past two to three months. It is a key test for diagnosing and monitoring diabetes.

What does the test measure?

HbA1c stands for glycated haemoglobin. When sugar is in your blood, some of it attaches to haemoglobin, the oxygen-carrying protein in red blood cells. The more sugar in your blood over time, the more attaches. Because red blood cells live for about three months, the HbA1c reading reflects your average blood sugar over that period, rather than a single moment.

How to prepare

An HbA1c test does not require fasting. You can eat and drink normally beforehand. This is one of its advantages over a fasting glucose test. The sample is a blood draw, and the result is usually available the same day.

What the result can mean

A higher HbA1c means your average blood sugar has been higher over the past few months. This is used to diagnose diabetes and to see how well treatment is working. A lower result generally means better blood sugar control. The target range depends on your individual situation, so your doctor will tell you what your number means for you.

When is it ordered?

Doctors order HbA1c to screen for diabetes, to confirm a diagnosis, and to monitor blood sugar control in people who already have diabetes. It is often checked every three months for people managing the condition, and as part of routine health checks for those at higher risk.

This article is for general information only and is not medical advice. Always discuss your results and any health concerns with your doctor.