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.
Please enter a valid number
HbA1c
7.0%
Diabetes
eAG (mg/dL) 154
eAG (mmol/L) 8.6
Classification scale
< 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
- · American Diabetes Association (ADA) 2024 Standards of Care: HbA1c < 5.7 % is normal; 5.7–6.4 % is prediabetes; ≥ 6.5 % meets the diagnostic threshold for diabetes (confirmed on a repeat test).
- · mg/dL ↔ mmol/L uses the glucose molar mass of 180.156 g/mol: 1 mmol/L ≈ 18.0182 mg/dL.
- · The conversion formula comes from the ADAG (A1c-Derived Average Glucose) study — 507 participants wearing CGM and doing 7-point self-monitoring over 13 weeks (Nathan et al., Diabetes Care 31(8):1473-1478, 2008).
- · Anaemia, haemoglobin variants, recent transfusion, chronic kidney disease and pregnancy can decouple A1C from average glucose. Clinical interpretation should always be left to a physician.
- · eAG is a conceptual average — it does not equal any single fasting or post-meal measurement. Treatment decisions still need both A1C trends and self-monitoring (SMBG / CGM).
- · This tool accepts HbA1c values 3–20 %, eAG 40–500 mg/dL or ~2–28 mmol/L. Calculation happens entirely in your browser — nothing is uploaded.
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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