HbA1c Result
HbA1c measures how much sugar has stuck to your red blood cells, which gives an average of your blood glucose over the past 2–3 months. It’s used to diagnose type 2 diabetes and prediabetes, and to track diabetes control. You don’t need to fast for it.
Quick answer: An HbA1c of 48 mmol/mol (6.5%) or more means diabetes, confirmed with a second test if you have no symptoms. 42–47 mmol/mol (6.0–6.4%) is prediabetes in Australia and the UK; US guidelines start at 39 (5.7%). Below 42 (6.0%) is normal. Anaemia, pregnancy and kidney disease can make results misleading.
What the test measures
Glucose in your blood sticks to haemoglobin, the oxygen-carrying protein in red blood cells. Red cells live about 3 months, so the percentage of “glycated” haemoglobin reflects your average sugar over that time, weighted towards the last few weeks. A single high or low day barely moves it.
Units: mmol/mol and %
Australia, the UK and New Zealand report mmol/mol, and many Australian reports show % as well. The US uses %.
- 39 mmol/mol = 5.7%
- 42 mmol/mol = 6.0%
- 48 mmol/mol = 6.5%
- 53 mmol/mol = 7.0%
- 64 mmol/mol = 8.0%
- 75 mmol/mol = 9.0%
Cut-offs in adults
- Under 42 mmol/mol (6.0%): normal in Australia and the UK.
- 42–47 mmol/mol (6.0–6.4%): prediabetes (the Australian Diabetes Society and RACGP), called non-diabetic hyperglycaemia in the UK.
- 39–47 mmol/mol (5.7–6.4%): prediabetes in the American Diabetes Association’s criteria, so a US report may flag a result that an Australian one wouldn’t.
- 48 mmol/mol (6.5%) or more: diabetes. Without symptoms, a second test on a different day is needed to confirm it.
- A fasting glucose of 7.0 mmol/L (126 mg/dL) or more, or a random glucose of 11.1 mmol/L (200 mg/dL) or more with symptoms, also diagnoses diabetes.
- A result under 48 doesn’t completely rule out diabetes, and a glucose tolerance test is sometimes used.
If you already have diabetes
- A common target is 53 mmol/mol (7.0%) or less, but targets are set individually: often higher for older or frail people, or anyone at risk of low sugars.
- HbA1c is usually checked every 3–6 months, and about 3 months after a change in treatment.
What a high result usually means
Common causes: type 2 diabetes and prediabetes, linked to family history, age, weight around the waist and inactivity. Steroid tablets and some antipsychotic medicines can also raise blood sugar.
Less common but important: type 1 diabetes or slow-onset autoimmune diabetes in adults (LADA), pancreas disease (pancreatitis, cystic fibrosis, haemochromatosis) and hormone conditions such as Cushing’s syndrome.
When HbA1c can mislead
- Falsely high: iron deficiency and B12 or folate deficiency (red cells live longer).
- Falsely low: recent bleeding or transfusion, red cells breaking down (haemolysis), recent iron or B12 treatment, pregnancy, advanced kidney disease, and some medicines such as dapsone.
- Either way: inherited haemoglobin variants, which some labs flag.
- Not used to diagnose diabetes in pregnancy, in children, or when sugar is rising fast, as in type 1 diabetes.
Symptoms
Most people with prediabetes or early type 2 diabetes have none. High sugar can cause thirst, passing a lot of urine, tiredness, blurred vision, thrush or slow-healing infections, and weight loss.
What happens next
- Normal: recheck according to your risk, usually every few years if you’re at higher risk.
- Prediabetes: weight loss of 5–10% and more activity roughly halve the risk of type 2 diabetes. Recheck HbA1c yearly. See prediabetes.
- 48 mmol/mol (6.5%) or more: a confirming test, then checks of kidneys, eyes, feet, blood pressure and cholesterol. See type 2 diabetes.
- Very high results, or weight loss in a young or slim person: tests for type 1 diabetes, including ketones.
Get urgent help (000 in Australia, or your local emergency number) for high sugar with vomiting, tummy pain, fast deep breathing, drowsiness or confusion: these can be signs of diabetic ketoacidosis. See a doctor the same day for thirst, passing lots of urine and weight loss you can’t explain, especially if you’re young or slim, or a glucose of 11.1 mmol/L (200 mg/dL) or more with symptoms: this can be type 1 diabetes, which needs prompt insulin. See your GP within a week or two for a new HbA1c of 48 mmol/mol (6.5%) or more without symptoms.
Practise reading results. Play Panelysis, the daily blood-test puzzle: a fictional patient, a real-looking panel, three guesses. More in medical games.
Common questions
What is a normal HbA1c?
In Australia and the UK, under 42 mmol/mol (6.0%) is normal for adults without diabetes. US guidelines use a lower cut-off of under 39 mmol/mol (5.7%). If you have diabetes, your target is set with your doctor, often 53 mmol/mol (7.0%) or less.
Is an HbA1c of 6.0% prediabetes?
In Australia and the UK, yes: 6.0–6.4% (42–47 mmol/mol) is the prediabetes range. In the US it starts lower, at 5.7% (39 mmol/mol). Either way, it’s a signal to act, and lifestyle changes work well.
How do I convert HbA1c % to mmol/mol?
Subtract 2.15 from the percentage, then multiply by 10.929. So 6.5% is about 48 mmol/mol and 7.0% is about 53 mmol/mol. Many Australian reports show both.
Do I need to fast for an HbA1c test?
No. HbA1c reflects your average sugar over the past 2–3 months, so a recent meal doesn’t change it. A fasting glucose test, often done at the same time, does need fasting.
Can prediabetes be reversed?
Often, yes. Losing 5–10% of your body weight and being more active roughly halves the chance of developing type 2 diabetes, and many people’s HbA1c falls back into the normal range.
Can anaemia affect HbA1c?
Yes. Iron and B12 deficiency can make HbA1c read falsely high, while bleeding, transfusion, haemolysis and recent iron treatment can make it read falsely low. If your HbA1c doesn’t match your glucose results, your doctor may use glucose tests instead.
How often should HbA1c be checked?
With diabetes, usually every 3–6 months, and about 3 months after a treatment change. With prediabetes, once a year. If you’re at higher risk but your result is normal, your GP will advise when to recheck.
Evidence and more information
- Pathology Tests Explained (RCPA): HbA1c
- RACGP and Diabetes Australia 2020: Management of type 2 diabetes, clinical summary (diagnostic cut-offs, repeat test, general target)
- Australian Diabetes Society 2020: Prediabetes position statement summary (HbA1c 6.0–6.4%, yearly testing)
- American Diabetes Association, Diabetes Care 2025: Standards of Care, diagnosis and classification of diabetes (A1C 5.7–6.4% prediabetes)
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