If you've recently had a blood test and your doctor mentioned your HbA1c, you might be wondering what on earth that number means — and whether you should be worried. You're not alone. HbA1c is one of the most common blood tests in the UK, but the result can feel confusing without context.
This guide explains exactly what HbA1c measures, how to read your result, and what steps you might take next.
What Is HbA1c?
HbA1c — also written as haemoglobin A1c or glycated haemoglobin — is a blood test that gives a picture of your average blood sugar (glucose) levels over the past 2 to 3 months.
Here's the key idea: when glucose circulates in your bloodstream, it sticks to haemoglobin (the protein in red blood cells that carries oxygen). The more glucose in your blood over time, the more it sticks. Because red blood cells live for roughly 3 months, the HbA1c test captures a rolling average of your blood sugar — not just a snapshot of today.
This makes it far more useful than a single fasting glucose reading for diagnosing and monitoring type 2 diabetes and prediabetes.
How Is HbA1c Measured?
In the UK and most of Europe, HbA1c is reported in millimoles per mole (mmol/mol). Some older documents or international sources use a percentage (%) — both are shown in the table below.
The test is a simple blood draw, usually from a vein in your arm, and does not require fasting beforehand.
HbA1c Results: What Do the Numbers Mean?
| HbA1c Level (mmol/mol) | HbA1c Level (%) | What It Means | What You Should Do |
|---|---|---|---|
| Below 42 mmol/mol | Below 6.0% | Normal — blood sugar is in the healthy range | Continue healthy lifestyle habits; routine check-ups as advised |
| 42–47 mmol/mol | 6.0–6.4% | Prediabetes — blood sugar is higher than normal but not yet diabetic | Lifestyle changes (diet, exercise, weight loss); GP follow-up; retest in 3–6 months |
| 48 mmol/mol or above | 6.5% or above | Type 2 diabetes — meets the diagnostic threshold | Confirm with a repeat test; begin treatment and monitoring plan with your GP |
| Below 48 mmol/mol (if already diagnosed) | Below 6.5% | Well-managed diabetes — on treatment and in target range | Continue current plan; discuss with your GP whether target needs adjusting |
| 48–58 mmol/mol (if already diagnosed) | 6.5–7.5% | Acceptable control — could be improved | Review diet, activity, or medication with your GP |
| Above 58 mmol/mol (if already diagnosed) | Above 7.5% | Poorly controlled diabetes — risk of complications is higher | Urgent review with GP or diabetes team; medication or lifestyle adjustment likely needed |
Note: Target ranges can vary depending on your age, other health conditions, and individual circumstances. Always discuss your specific result with your GP or diabetes nurse.
What Can Affect Your HbA1c Result?
HbA1c is a reliable test, but certain factors can make the result misleading:
- Anaemia or haemoglobin variants — conditions affecting red blood cells can artificially lower or raise the result
- Pregnancy — HbA1c is less reliable during pregnancy; different tests are used
- Recent blood transfusions — can affect the reading
- Kidney disease or liver disease — may alter haemoglobin turnover
- Certain ethnic backgrounds — some populations have haemoglobin variants that affect accuracy
If any of these apply to you, your doctor may use an alternative test — such as a fasting plasma glucose test or an oral glucose tolerance test (OGTT) — to get a clearer picture.
I'm in the Prediabetes Range — Should I Be Worried?
A prediabetes result (42–47 mmol/mol) is not a diagnosis of diabetes, but it is an important warning sign. The good news is that prediabetes is often reversible with lifestyle changes.
Research consistently shows that the following can bring HbA1c back into the normal range:
- Losing 5–10% of body weight if you're overweight
- Increasing physical activity — aim for at least 150 minutes of moderate exercise per week
- Reducing refined carbohydrates and sugary foods
- Stopping smoking, which raises cardiovascular risk alongside blood sugar issues
Your GP may refer you to the NHS Diabetes Prevention Programme, a free structured programme designed specifically for people with prediabetes in England.
My Result Shows Type 2 Diabetes — What Happens Next?
A single HbA1c result of 48 mmol/mol or above will usually be confirmed with a second test before a formal diagnosis is made (unless you have clear symptoms such as excessive thirst, frequent urination, or unexplained weight loss).
If the diagnosis is confirmed, your GP will work with you to create a management plan that may include:
- Lifestyle advice on diet and exercise
- Medication, most commonly metformin to start
- Regular HbA1c monitoring — typically every 3 to 6 months until stable, then every 6 to 12 months
- Referral to a diabetes education programme such as DESMOND or X-PERT
Type 2 diabetes is a serious condition, but with the right management it is very possible to live well and reduce your risk of complications.
How Often Should I Have an HbA1c Test?
| Situation | Recommended Frequency |
|---|---|
| No known blood sugar issues | Every 1–3 years if you have risk factors (obesity, family history, age 45+) |
| Prediabetes | Every 3–6 months, or as advised by your GP |
| Newly diagnosed type 2 diabetes | Every 3 months until stable |
| Well-managed type 2 diabetes | Every 6–12 months |
| Type 1 diabetes | Every 3–6 months |
Key Takeaways
- HbA1c measures your average blood sugar over 2–3 months, making it the gold standard for diagnosing and monitoring diabetes.
- A result below 42 mmol/mol is normal. 42–47 mmol/mol indicates prediabetes. 48 mmol/mol or above meets the threshold for a type 2 diabetes diagnosis.
- If your result is in the prediabetes range, lifestyle changes can make a significant difference.
- If you're already diagnosed with diabetes, your target HbA1c will be set by your care team based on your individual circumstances.
- Always discuss your result with your GP — numbers only tell part of the story.
Frequently Asked Questions
Can I lower my HbA1c quickly? HbA1c reflects 2–3 months of blood sugar history, so changes take time to show up. Most people see meaningful improvements within 3 months of sustained dietary and lifestyle changes.
Is HbA1c the same as a blood sugar reading? No. A blood sugar (glucose) reading — such as from a finger-prick test — shows your blood sugar at a single moment in time. HbA1c shows your average over months, which is more useful for long-term management.
Can I have a normal HbA1c but still have diabetes? In some cases, yes — particularly in early type 1 diabetes or where haemoglobin variants affect the test. If your symptoms suggest diabetes but your HbA1c is normal, your doctor may order additional tests.
Does a high HbA1c always mean type 2 diabetes? Not necessarily. Your doctor will consider the full clinical picture, including symptoms, other test results, and your medical history, before making a diagnosis.
This article is for informational purposes only and does not constitute medical advice. Always consult your GP or healthcare provider about your individual results and health needs.
