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HbA1c ↔ Average Blood Glucose (eAG) Converter

Glycated haemoglobin (HbA1c, also A1C) reflects your average blood-sugar level over the past 2–3 months. Enter HbA1c to get the estimated average glucose (eAG) shown in both mg/dL and mmol/L — or go the other way, entering eAG to recover the A1C. The conversion uses the regression equation from the 2008 ADAG study (eAG mg/dL = 28.7 × A1C − 46.7) and classifies the result against the American Diabetes Association 2024 Standards of Care.

HbA1c

7.0%

Diabetes

eAG (mg/dL) 154

eAG (mmol/L) 8.6

Classification scale

Normal
< 5.7 %
Prediabetes
5.7–6.4 %
Diabetes
≥ 6.5 %

Regression: eAG (mg/dL) = 28.7 × A1C − 46.7 (ADAG 2008). Classification: ADA 2024 Standards of Care.

Formula

eAG (mg/dL) = 28.7 × HbA1c (%) − 46.7 eAG (mmol/L) = eAG (mg/dL) ÷ 18.0182 HbA1c (%) = (eAG (mg/dL) + 46.7) ÷ 28.7

Frequently asked

What's the difference between HbA1c and a fasting blood-glucose test?

A fasting glucose test only captures the blood-sugar concentration at the moment of the draw, so it swings with recent food, exercise and stress. HbA1c reflects the average amount of glucose bound to red-blood-cell haemoglobin over the past 2–3 months (red blood cells live about 120 days), so short-term fluctuations matter much less. In clinical practice fasting glucose, the oral glucose tolerance test and HbA1c all have a role: HbA1c tracks long-term control; fasting/post-meal glucose fine-tunes day-to-day therapy; the OGTT is best for screening prediabetes.

My HbA1c is 7 %. What's my estimated average glucose?

Using the ADAG regression: eAG = 28.7 × 7 − 46.7 = 154 mg/dL, which is about 8.6 mmol/L. This is a long-term "concept average" over the past 2–3 months — it does not mean your fasting or post-meal numbers always sit there. The ADA suggests an HbA1c target below 7 % for most non-pregnant adults with diabetes (your clinician may set a tighter or looser goal); 7 % is close to but not quite at the target.

Why do different countries report blood glucose in mg/dL or mmol/L?

mg/dL is a mass concentration (milligrams per decilitre) — used in the United States, parts of Brazil and France, and many private labs in Hong Kong. mmol/L is a molar concentration (millimoles per litre) — recommended by the WHO / IFCC and standard in the UK, Canada, Australia, most of Europe and Hong Kong public hospitals. Since glucose has a molar mass of 180.156 g/mol, 1 mmol/L = 18.0182 mg/dL — a pure unit conversion. The general trend has been a slow migration toward mmol/L.

When is HbA1c unreliable as a measure?

HbA1c becomes unreliable whenever red-cell lifespan or haemoglobin itself is altered: (1) iron, B12 or folate deficiency can falsely elevate HbA1c; (2) haemolytic anaemia, recent bleeding/transfusion or shortened red-cell life can falsely lower it; (3) haemoglobin variants (HbS, HbC, HbE — common in African, South-East Asian and Mediterranean ancestry) can interfere with the assay; (4) HbA1c may under-estimate average glucose in the second and third trimesters of pregnancy. In these cases clinicians turn to fructosamine, glycated albumin or CGM-derived metrics instead.

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