HbA1c — 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.
What the numbers mean
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:
| Result (mmol/mol) | Result (%) | What it means | Status |
|---|---|---|---|
| Below 42 | Below 6.0% | Normal blood sugar control | Normal |
| 42–47 | 6.0–6.4% | Prediabetes (impaired glucose regulation) | Monitor |
| 48 or above | 6.5% or above | Type 2 diabetes (if confirmed on repeat test) | Act |
What "normal" actually means
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, are carrying excess weight around your abdomen, or have other metabolic risk factors such as elevated triglycerides or low HDL cholesterol.
The prediabetes range: 42–47 mmol/mol
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: dietary carbohydrate quality and quantity, physical activity (particularly after meals), sleep quality, and stress. Even a 5–7% reduction in body weight, if you are overweight, can bring HbA1c back into the normal range.
If your result is 48 or above
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.
Why tracking HbA1c over time matters
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 — longitudinally. Rather than asking "is this result normal?", it asks "is this result moving in the right direction for you?"
What to ask your GP
- What was my HbA1c last time, and has it changed?
- What range should I be aiming for, given my personal risk factors?
- Would a fasting glucose or oral glucose tolerance test give me more information?
- Am I eligible for the NHS Diabetes Prevention Programme?
Track this marker over time, not just today
biomarkr keeps every result in one place and shows you the direction each marker is heading — free for your first year.