HbA1cGlycated haemoglobin · Haemoglobin A1c

HbA1c (glycated haemoglobin) reflects the proportion of your haemoglobin — the oxygen-carrying protein in red blood cells — that has sugar stuck to it. Because red cells live for around three months, it acts as a running average of your blood sugar over that period.

It matters because, unlike a single glucose reading, HbA1c smooths out day-to-day spikes and dips, which makes it the standard marker for tracking longer-term glucose control and for screening for prediabetes and diabetes.

In practice, HbA1c is read together with fasting glucose; conditions that change red-cell lifespan (such as anaemia) can distort it, so it is interpreted in context rather than as a lone number.