HbA1c (Glycated Haemoglobin)

HbA1c (glycated haemoglobin) reflects your average blood sugar level over the past two to three months. It measures the amount of glucose attached to haemoglobin, the oxygen-carrying protein in red blood cells. Because red cells live for around three months, HbA1c gives a longer-term picture of blood sugar control than a single glucose measurement, which only captures one moment in time.

What it can help assess

• Diagnosing diabetes and prediabetes: HbA1c is a key test for identifying diabetes and the raised-risk state known as prediabetes
• Monitoring diabetes: for people already diagnosed, it is the main test used to track how well blood sugar is being controlled over time
• Assessing long-term risk: better long-term control, reflected in a lower HbA1c, reduces the risk of diabetes-related complications

An important note on interpretation

Because HbA1c depends on red blood cells, certain conditions that affect these cells, such as anaemia, some inherited haemoglobin variants, or recent significant blood loss, can affect the accuracy of the result. In these situations HbA1c is interpreted with care and sometimes alongside other tests. Any abnormal result should be discussed with your GP, who can interpret it in context and advise on any further testing or management.

Why it matters

Raised blood sugar often causes no symptoms in its early stages, so many people have diabetes or prediabetes without knowing. HbA1c provides a reliable, longer-term measure of blood sugar control, helping to detect problems early and to monitor and manage diabetes effectively over time.