What A1C measures
A1C (also written HbA1c) reflects your average blood sugar over the past two to three months. It works by measuring the percentage of your haemoglobin — the oxygen-carrying protein in red blood cells — that has glucose attached. The higher your average blood sugar, the higher that percentage.
Because it averages months of data, A1C is far more stable than a single finger-prick reading, which is why it's the standard test for diagnosing and monitoring diabetes.
A1C and average glucose
Your A1C percentage maps directly to an estimated average glucose (eAG) in the same units as a home meter. This calculator uses the widely adopted formula eAG (mg/dL) = 28.7 × A1C − 46.7, and converts to mmol/L by dividing by 18. Switch the direction to turn an average glucose reading back into an A1C.
The diagnostic ranges
| A1C | Category |
|---|---|
| Below 5.7% | Normal |
| 5.7–6.4% | Prediabetes |
| 6.5% and above | Diabetes range |
Lowering your A1C
For many people, gradual, sustainable changes move A1C in the right direction: losing excess weight, moving more, choosing higher-fibre carbohydrates, and getting enough sleep. Our calorie and macro calculators can help you build a supportive eating plan — alongside, not instead of, your medical care.
Helpful tools
Track day-to-day glucose between A1C tests.
View options →See how food and activity affect your glucose in real time.
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Frequently asked questions
What is a normal A1C level?
Below 5.7% is considered normal. 5.7–6.4% indicates prediabetes, and 6.5% or higher on two tests is in the diabetes range, per the American Diabetes Association.
How does A1C relate to average glucose?
A1C maps to an estimated average glucose (eAG). The formula is eAG (mg/dL) = 28.7 × A1C − 46.7. For example, a 7% A1C is roughly 154 mg/dL (8.6 mmol/L).
How often should A1C be checked?
Typically every 3–6 months for people managing diabetes, and periodically for screening in at-risk adults. Your provider sets the right interval for you.
Can I lower my A1C naturally?
Often, yes — through weight loss, regular activity, higher-fibre food choices and good sleep. Always make changes alongside, not instead of, your prescribed care.