HbA1c: what the number means

HbA1c measures how much sugar has attached to haemoglobin in your red blood cells. Because those cells live for about three months, it reflects your average blood sugar over that time, not just this morning.

Widely used guidance treats 5.7% to 6.4% as the prediabetes range, and 6.5% or higher as the diabetes range, usually confirmed with a second test. Some bodies, including NICE in the UK, start the higher-risk range at 6.0%.

One result is a starting point. Iron deficiency, recent blood loss and some haemoglobin variants can shift HbA1c, so a doctor may pair it with a fasting glucose test. The useful thing to watch is the direction across draws, read together with your weight, waist and family history.