In short
- Prediabetes is an in-between state between controlled sugar and type 2 diabetes. It can last for years and it is reversible.
- The American criterion is HbA1c 5.7–6.4%; the European and global one is often 6.0–6.4%. The difference is not an error, but a different choice of threshold.
- The same state is also picked up by fasting glucose of 6.1–6.9 mmol/L. A glucose tolerance test picks it up with a value of 7.8–11.0 mmol/L after two hours.
- The best-proven measure is losing 7% of body weight and 150 minutes of activity a week. In a large study it cut progression to diabetes by 58%.
- HbA1c is falsely low in anaemia and after a transfusion, and falsely high in iron deficiency. In these situations, read glucose instead.
Between controlled sugar and type 2 diabetes there is an in-between period. It lasts for years, causes no symptoms, and goes unnoticed without measuring. That period is the only one in which the path can still be reversed without medicines.
What your number means
HbA1c tells you what share of the haemoglobin in your red blood cells has bound sugar. Red cells live about three months, so HbA1c is the average sugar of the last two to three months. You cannot improve it with a one-day diet before the blood draw.
| Result | Meaning | What follows |
|---|---|---|
| HbA1c below 5.7% glucose below 6.1 mmol/L | Controlled. | Re-test every few years, sooner with risk factors. |
| HbA1c 5.7–6.4% glucose 6.1–6.9 mmol/L | Prediabetes, or increased risk. | Lifestyle measures, re-test in 3–6 months. |
| HbA1c 6.5% or more glucose 7.0 mmol/L or more | Suspected type 2 diabetes. | Talk to your doctor. The diagnosis requires confirmation with a second measurement. |
A single value is never a diagnosis. A doctor diagnoses diabetes, usually from two measurements or from one measurement with clear symptoms.
Why there are two cut-offs for prediabetes
The American Diabetes Association uses a lower cut-off of 5.7%. The World Health Organization and part of European practice use 6.0%. The lower cut-off captures more people and finds more of those who will go on to develop diabetes. The higher cut-off is more specific and labels fewer people as at risk unnecessarily.
For a practical decision the difference does not matter much. If your HbA1c is between 5.7 and 6.4%, you are on a path worth reversing, whichever cut-off your laboratory uses. What matters is what you do, not which organisation puts you in which group.
Who benefits most from testing
- Excess weight or a waist circumference over 94 cm in men and over 80 cm in women.
- Diabetes in the family, especially in parents or siblings.
- Diabetes in pregnancy in the past, or a baby born weighing over 4 kg.
- Polycystic ovary syndrome.
- High blood pressure, low HDL or raised triglycerides.
- A sedentary lifestyle after 40, even without other factors.
If you are under 40 and do not fall into any of these groups, yearly testing is not necessary. A one-time measurement as a baseline, however, makes sense for everyone.
What is proven to work
This is one of the few areas where we have solid numbers from large studies, not just recommendations.
| Measure | What it brings | How much |
|---|---|---|
| Losing 7% of body weight and 150 minutes of moderate exercise a week | The best-proven measure. In the Diabetes Prevention Program study it cut progression to diabetes over three years. | by 58% |
| Strength training, two to three times a week | Muscle is the biggest consumer of sugar. It works even without weight loss. | complements the above |
| Fewer sugary drinks and liquid sugar | The quickest change with the biggest effect on daily swings. | immediate effect |
| More fibre (legumes, whole grains, vegetables) | Slows the rise in sugar after a meal and improves fullness. | gradual |
| Sleeping 7–8 hours | Chronic lack of sleep worsens insulin sensitivity. | often overlooked |
For some people with prediabetes the doctor also prescribes a medicine, most often metformin. This is more likely in younger people, with a higher body mass index, and after diabetes in pregnancy. That is a doctor's decision, not one made from a self-paid report.
Honestly: no dietary supplement is proven to prevent type 2 diabetes. Chromium, cinnamon and berberine are often marketed with that promise. The evidence is weak and inconsistent. What works is weight, movement and sleep.
When HbA1c misleads
HbA1c measures haemoglobin, so it is thrown off by anything that changes the lifespan of red blood cells:
- Falsely low in anaemia due to red cell breakdown, after a recent transfusion, after bleeding, and in pregnancy.
- Falsely high in iron deficiency, because red cells live longer.
- Unreliable with some inherited haemoglobin variants and in advanced kidney disease.
That is why HbA1c should never be read on its own. Look at it together with fasting glucose and a complete blood count (CBC). Then the app can warn you when the interpretation is questionable.
When to re-test
After a lifestyle change, the earliest meaningful re-test is after three months, because HbA1c reflects the average of the last two to three months. Any sooner and you will still be measuring the old period. If the result is in the prediabetes range and you do not take any measures, a yearly re-test makes sense.
Fasting glucose moves faster. You can check it after six to eight weeks if you want interim feedback.
Frequently asked questions
What does HbA1c 6.0% mean?
It puts you in the prediabetes range by both the American and the global criterion. It is not diabetes and not a reason for a medicine. But it is a clear sign that the path is worth reversing now, while it is still reversible.
Is prediabetes reversible?
For a large share of people, yes. In the Diabetes Prevention Program study, people lost 7% of body weight and did 150 minutes of activity a week. This cut progression to diabetes by 58% over three years.
Do I need to fast for HbA1c?
No. HbA1c is the average of the last two to three months and your last meal does not change it. If glucose or lipids are measured in the same panel, though, fasting applies to the whole panel.
Why is my glucose normal but my HbA1c raised?
Fasting glucose is a momentary value, HbA1c an average. If your sugar spikes after meals and settles by morning, the morning glucose will look fine, but HbA1c will reveal it.
Does any supplement help?
None is proven to prevent diabetes. Chromium, cinnamon and berberine have weak and inconsistent evidence. Weight, movement and sleep have solid evidence.
Sources: ADA Standards of Care — criteria for prediabetes (HbA1c 5.7–6.4%) · WHO — criteria for impaired fasting glucose and impaired glucose tolerance · Diabetes Prevention Program (DPP) — 58% reduction in progression to diabetes with 7% weight loss and 150 minutes of exercise a week · IFCC — HbA1c standardisation and conditions that distort it · EASD/ESC — metabolic risk and management.
