The NHS uses 48 mmol/mol as its diabetes threshold. What does your number mean if you sit below it, and what counts as prediabetes? A plain English guide for UK patients.
HbA1c, or glycated haemoglobin, is the most important single marker for blood sugar control. Unlike a fasting glucose test, which shows where your blood sugar is right now, HbA1c reflects your average blood sugar over the past two to three months. That makes it far more useful for understanding your metabolic health over time.
In the UK, HbA1c is reported in mmol/mol, millimoles per mole. Some older reports use a percentage. The two scales measure the same thing, just differently. The NHS uses the following thresholds:
| mmol/mol | Percent | What it means | Status |
|---|---|---|---|
| Below 42 | Below 6.0% | Normal blood sugar control. | Normal |
| 42 to 47 | 6.0 to 6.4% | Prediabetes, also called impaired glucose regulation. | Monitor |
| 48 or above | 6.5% or above | Type 2 diabetes, if confirmed on a repeat test. | Act |
If your result is reported as a percentage, for example 5.7%, multiply by 10.929 to get the mmol/mol equivalent, or use the NHS conversion tool. Most UK labs now report in mmol/mol.
A result below 42 mmol/mol means your average blood sugar has been within a healthy range over the past few months. But normal is not the same as optimal. Research consistently shows that metabolic risk increases gradually across the normal range: a result of 40 mmol/mol carries a different long term risk profile than one of 30 mmol/mol, even though both are technically normal.
This is particularly relevant if you have a family history of type 2 diabetes, carry excess weight around your abdomen, or have other metabolic risk factors such as elevated triglycerides or low HDL cholesterol.
A result in the prediabetes range does not mean you will develop type 2 diabetes. It means your blood sugar regulation is under strain, and that lifestyle changes now can make a significant difference. The NHS Diabetes Prevention Programme is available to people in this range and has strong evidence behind it.
Key lifestyle factors that influence HbA1c include the quality and quantity of carbohydrate in your diet, physical activity, particularly after meals, sleep quality and stress. If you are overweight, even a 5 to 7% reduction in body weight can bring HbA1c back into the normal range.
A single result of 48 mmol/mol or above is not sufficient for a diagnosis of type 2 diabetes unless you have symptoms. The NHS requires a second confirmatory test on a different day. If your result is significantly elevated, above 58 mmol/mol, or you have symptoms such as increased thirst, frequent urination or unexplained weight loss, speak to your GP promptly.
If your HbA1c is 48 mmol/mol or above, or it has risen significantly since your last test, book an appointment with your GP. Do not wait for your next routine check.
A single HbA1c result tells you where you are today. A series of results tells you which direction you are heading. An HbA1c of 40 mmol/mol that has risen from 32 over two years is a different situation from one that has been stable at 40 for five years. The trend is often more informative than the number itself.
This is why biomarkr tracks your HbA1c, and every other marker, over time. Rather than asking whether a result is normal, it asks whether the result is moving in the right direction for you.
The trend tells you more than the number. biomarkr tracks your HbA1c across every test and shows you which way it is heading. Free for your first year.
Join early access →Thresholds and guidance in this article are drawn from NHS sources and NICE Clinical Knowledge Summaries. Your own lab report ranges always take precedence.
Educational purposes only · not medical advice · always speak to your GP or a qualified clinician about your results