What it measures
- HbA1c (glycated haemoglobin)
What is HbA1c?
Sugar (glucose) in your blood sticks to haemoglobin in your red blood cells. Because red cells live for around three months, measuring how much haemoglobin has sugar attached, your HbA1c, shows your average blood sugar over the past 2–3 months. Unlike a single glucose reading, it isn’t affected by what you ate this morning, so you don’t need to fast.
What do HbA1c results mean?
In the UK, results are given in mmol/mol:
HbA1c | What it suggests |
|---|---|
Below 42 mmol/mol | Within the normal range |
42–47 mmol/mol | Prediabetes: a higher risk of type 2 diabetes |
48 mmol/mol or above | Suggests diabetes, which a doctor will confirm |
Prediabetes is common and often reversible. Small changes to diet, activity and weight can bring your HbA1c back into the normal range, so an early result is valuable. We’ll recommend you share a raised result with your GP.
Who it’s for
- A family history of type 2 diabetes
- Feeling very thirsty, passing urine more often or unusual tiredness
- Being overweight, or of South Asian, Black African or African-Caribbean heritage
- Previous gestational diabetes
- Monitoring known diabetes or prediabetes
How to prepare
- Drink plenty of water beforehand; it makes the sample quicker and easier to take.
- You don’t need to fast.
Diabetes (HbA1c) Blood Test: your questions
Do I need to fast for an HbA1c test?
No. HbA1c reflects your average blood sugar over 2–3 months, so you can eat and drink normally beforehand.
Is HbA1c accurate for everyone?
Mostly, but it can be less reliable in pregnancy, after recent blood loss or a transfusion, with some types of anaemia and with certain haemoglobin variants. Let us know if any of these apply to you.
Information on this page is general and doesn’t replace advice from your GP, midwife or consultant. If you feel unwell or are worried about symptoms, contact your GP, call NHS 111 or, in an emergency, 999.