What is HbA1c (A1C)?
HbA1c — also called A1C or glycated haemoglobin — measures how much sugar is attached to the haemoglobin in your red blood cells. Because red blood cells live for about three months, HbA1c shows your average blood sugar over the past 2–3 months, not just today. Doctors use it to diagnose prediabetes and type 2 diabetes and to check how well diabetes is controlled.
Results are reported as a percentage (common in the USA, UAE and Pakistan) or in mmol/mol (the IFCC unit used in the UK and Europe). This free A1C calculator converts between both and to your estimated average glucose (eAG).
How the A1C calculator works
- eAG (mg/dL) = 28.7 × A1C − 46.7 — from the international ADAG study (Nathan et al., 2008), adopted by the American Diabetes Association.
- eAG (mmol/L) = eAG (mg/dL) ÷ 18.
- IFCC (mmol/mol) = (A1C % − 2.15) × 10.929.
Example: an HbA1c of 7% equals an average glucose of about 154 mg/dL (8.6 mmol/L) and 53 mmol/mol.
A1C chart: normal, prediabetes and diabetes
| HbA1c % | mmol/mol | Average glucose | Category |
|---|---|---|---|
| Below 5.7% | Below 39 | Below 117 mg/dL (6.5 mmol/L) | Normal |
| 5.7 – 6.4% | 39 – 47 | 117 – 137 mg/dL (6.5 – 7.6 mmol/L) | Prediabetes |
| 6.5% or higher | 48 or higher | 140 mg/dL (7.8 mmol/L) or higher | Diabetes range |
Quick A1C conversion table
| A1C | eAG mg/dL | eAG mmol/L |
|---|---|---|
| 5% | 97 | 5.4 |
| 6% | 126 | 7.0 |
| 7% | 154 | 8.6 |
| 8% | 183 | 10.2 |
| 9% | 212 | 11.8 |
| 10% | 240 | 13.4 |
Benefits of knowing your A1C
- Early warning: prediabetes can often be reversed with diet, activity and modest weight loss.
- Big-picture control: one test reflects three months, so a single high or low reading does not mislead you.
- Lower complication risk: each 1% drop in HbA1c is linked with a substantial fall in eye, kidney and nerve complications.
- Measure what your diet is doing — retest every 3 months after changes.
Health warnings
- A diagnosis of diabetes needs a repeat test or another test (such as fasting glucose) — do not self-diagnose.
- HbA1c can be falsely low or high with anaemia, recent blood loss or transfusion, haemoglobin variants (for example thalassaemia trait, common in South Asia and the Middle East), kidney disease and pregnancy.
- Never change diabetes medicine based on a calculator — talk to your doctor.
- HbA1c does not show daily highs and lows; people on insulin also need finger-prick or sensor readings.
How to lower your A1C with food
Swap white rice, white bread and sugary drinks for wholegrains, dal and water; fill half your plate with vegetables; include protein at every meal; and walk for 10–15 minutes after meals. Check foods with the glycemic load calculator and your daily carb target, and read our insulin resistance diet and diabetes-friendly breakfast ideas.
Frequently asked questions
What is a normal A1C level?
Below 5.7% (39 mmol/mol) is normal. 5.7–6.4% (39–47 mmol/mol) is prediabetes, and 6.5% (48 mmol/mol) or higher on two tests indicates diabetes.
What average blood sugar is an A1C of 7?
An A1C of 7% equals an estimated average glucose of about 154 mg/dL or 8.6 mmol/L.
How do I convert A1C to mmol/mol?
Subtract 2.15 from your A1C percentage and multiply by 10.929. For example, (7 − 2.15) × 10.929 ≈ 53 mmol/mol.
How quickly can I lower my A1C?
Because A1C reflects about three months, changes show at the next test. Many people see a drop of 0.5–1% or more within 3 months of consistent diet, activity and medication changes.
What A1C target should I aim for with diabetes?
Many adults with diabetes aim for below 7% (53 mmol/mol), but your doctor may set a higher or lower target depending on your age, medicines and risk of low blood sugar.
Sources
- Nathan DM, et al. Translating the A1C assay into estimated average glucose values (ADAG). Diabetes Care 2008;31:1473–1478.
- American Diabetes Association. Standards of Care in Diabetes — Diagnosis and classification.
- WHO. Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus. 2011.