What is HbA1c and how does it assess your diabetes risk? What the normal, prediabetes and diabetes ranges mean, and why prediabetes is often reversible.
HbA1c is the standard blood test used to assess your average blood sugar levels and your risk of type 2 diabetes. Unlike a finger-prick glucose reading, which only shows your blood sugar at that exact moment, HbA1c reflects your average blood sugar over roughly the previous 2–3 months: making it a much more reliable long-term indicator.
How does HbA1c work?
Glucose in your bloodstream attaches to haemoglobin (the protein in red blood cells that carries oxygen) in a process called glycation. The more glucose circulating in your blood, the more it attaches. Because red blood cells live for around three months, HbA1c effectively captures a rolling average of your blood sugar over that period, rather than a single snapshot.
What do the results mean?
HbA1c is usually reported in mmol/mol (with an equivalent percentage). Broadly:
- Normal range: typically below 42 mmol/mol (6.0%).
- Prediabetes: typically 42–47 mmol/mol (6.0–6.4%), indicating higher-than-normal blood sugar that hasn’t yet reached diabetic levels.
- Diabetes range: typically 48 mmol/mol (6.5%) or above.
These are general UK guideline thresholds; your result will be given alongside the reporting laboratory’s specific ranges, and diagnosis is always confirmed by a doctor rather than a single test result.
Why prediabetes matters
Prediabetes means your blood sugar is higher than normal but not yet in the diabetic range. It’s an important result because, unlike a diabetes diagnosis, prediabetes is often reversible through lifestyle changes; diet, physical activity and weight management, giving you a genuine window to change your trajectory before type 2 diabetes develops.
Who should consider testing?
HbA1c is worth considering if you have a family history of diabetes, are carrying excess weight (particularly around the waist), have persistent tiredness or thirst, are over 40, or simply want a baseline as part of general health monitoring.
HbA1c vs a fasting glucose test
A fasting glucose test measures your blood sugar at a single point in time (after fasting), while HbA1c reflects your average over months and doesn’t require fasting. Both have their uses, but HbA1c’s stability and convenience make it the preferred routine screening test in most cases.
Getting tested
HbA1c is included in our Diabetes & Blood Sugar (HbA1c) Test and our General Health & Wellbeing Screen.
Not sure which test to choose? Use our free Test Finder for a personalised recommendation in under a minute.
Frequently asked questions
Do I need to fast for an HbA1c test?
No; unlike a fasting glucose test, HbA1c doesn’t require fasting, which is one of its practical advantages.
Can HbA1c diagnose diabetes on its own?
It’s a key part of diagnosis, but a doctor will consider your result alongside your symptoms and, sometimes, a repeat test before confirming a diagnosis.
Is prediabetes reversible?
Often, yes; lifestyle changes such as diet and exercise can bring blood sugar back into the normal range for many people.
How often should I check my HbA1c?
Annually is a sensible default for most adults, or more frequently if you have prediabetes, diabetes, or specific risk factors; discuss the right interval with your GP.
How quickly will I get my results?
Most results are available within 1–2 working days and are reviewed by a GMC-registered doctor before you receive them.
Important note
This article is for general education only and is not medical advice or a diagnosis. Diabetes and prediabetes should be diagnosed and managed by your GP. Trupoint Health blood tests are analysed by a UKAS-accredited laboratory and reviewed by a GMC-registered doctor.
Medically reviewed by: ____________ (GMC-registered), pending review.
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