HbA1c
Glycated Haemoglobin
What this test measures
HbA1c measures your average blood sugar level over the past 2 to 3 months. It shows how much sugar has attached to your red blood cells. This test is mainly used to check for diabetes or to see how well your diabetes is being controlled.
Understanding the numbers
Typical range: 20-41 mmol/mol (below 6.0%)
42-47 mmol/mol means you are at higher risk of diabetes (pre-diabetes). 48 mmol/mol or above suggests diabetes. UK uses mmol/mol, not percentage.
- Normal: 20–41 mmol/mol
- Pre-diabetes: 42–47 mmol/mol
- Diabetes: 48–120 mmol/mol
Key numbers
- 42 mmol/mol — Pre-diabetes starts
- 48 mmol/mol — Diabetes threshold
- 58 mmol/mol — NICE: intensify treatment
- 75 mmol/mol — Very raised — contact GP urgently
Thresholds 42, 48 and 58 mmol/mol are from NICE CKS (diabetes diagnosis) and NICE NG28 (treatment targets). The 75 mmol/mol marker is clinician guidance, not a NICE-named threshold.
Ranges can vary slightly between laboratories — your report may show slightly different numbers. This page does not read or interpret your result; your GP looks at it alongside your history and other tests.
What a higher-than-normal result can mean
- Your blood sugar has been too high over recent months
- You may have diabetes or pre-diabetes
- If you have diabetes, your treatment may need adjusting
- You may need to make changes to your diet or lifestyle
When not to wait
If you know or suspect your blood sugar is high and you feel unwell, don't wait for your next appointment.
- Being sick or unable to keep fluids down
- Stomach pain
- Breathing faster than usual or a fast heartbeat
- Feeling drowsy or struggling to stay awake
- Fruity-smelling breath (like pear drops)
- Feeling confused or having trouble concentrating
- High ketones in blood or urine
Call NHS 111 for urgent advice, or 999 if someone is seriously unwell.
Questions you could ask your GP
- What is my target HbA1c level, and how often should I have it checked?
- Are there any changes to my diet or lifestyle that could help improve my result?
- Do I need to be referred to a diabetes nurse or dietitian?
- Should I be checking my blood sugar at home as well?
Example stories
These are made-up examples to show how results are talked about in real appointments. They are not real patients.
Routine health check
Meera had an HbA1c of 38 mmol/mol as part of her routine NHS health check. This sits comfortably in the normal range.
What the GP said: “Your blood sugar control looks good. No action needed — we'll check again in about five years unless anything changes.”
A normal HbA1c doesn't need treatment. It's reassuring, but it doesn't mean you can stop thinking about lifestyle — family history, weight, and activity all still matter for staying there.
Family history of diabetes
Raj's HbA1c came back at 45 mmol/mol — in the pre-diabetes range. He wasn't surprised: his father had Type 2 diabetes, and he'd put on weight working from home.
What the GP said: “This isn't diabetes, but your body is heading that way. The good news is that at this stage, changes to diet, weight and activity can bring it back down. I'd like to repeat the test in six months.”
What happened next: He joined the NHS Diabetes Prevention Programme, cut down on sugary drinks, and started walking 30 minutes most days. Six months later his HbA1c was 41 — back in the normal range.
Pre-diabetes is a warning, not a diagnosis. It's one of the few places in medicine where lifestyle changes alone can reverse the trend. Ask your GP about the NHS Diabetes Prevention Programme if this is you.
Tired, thirsty, going to the toilet a lot
Priya had been feeling tired and noticed she was drinking a lot of water and going to the toilet more. Her GP organised a blood test. Her HbA1c was 58 mmol/mol — a new diagnosis of Type 2 diabetes.
What the GP said: “This is Type 2 diabetes. It's a long-term condition, but very manageable. We're going to start a tablet called metformin, refer you to a diabetes education programme, and check your eyes, feet and kidneys. We'll repeat this test in three months.”
What happened next: Priya started metformin, attended the DESMOND course, and began walking daily. At three months her HbA1c was 52. Her GP was pleased and kept the same treatment plan.
A first HbA1c of 48 or above usually means diabetes — but your GP will normally repeat the test to confirm. Treatment is a combination: tablets, education, annual checks, and lifestyle. It is not a death sentence; most people with Type 2 live well for decades.
Known diabetes, annual review
David has had Type 2 diabetes for ten years. His HbA1c had been stable around 55, but at his annual review this year it was 78 — a significant rise.
What the GP said: “Your blood sugar control has slipped. This level increases your risk of eye, kidney, nerve and heart problems over time. We need to review what's happening — your tablets may need adjusting, and we should talk about adding insulin or a newer injectable medication.”
What happened next: David's GP added a second medication and referred him to the diabetes specialist nurse. They found he'd been skipping metformin because of tummy upset — a slow-release version fixed that. Six months later his HbA1c was 62, and still heading down.
A rising HbA1c in someone with known diabetes is a signal that something has changed — medication, weight, other illness, or just the natural course of the condition. It isn't a failure. It's a reason to go back to your GP and adjust the plan.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.