Estimated average glucose from HbA1c
Translate HbA1c (IFCC mmol/mol or %) into average glucose in mmol/L (ADAG)
Sources last checked: 2026-10-13
Estimated average glucose from HbA1c
Translate HbA1c (IFCC mmol/mol or %) into average glucose in mmol/L (ADAG)
Population average: the SD of the prediction error was 0.87 mmol/L, and HbA1c is misleading with altered red-cell lifespan (haemolysis, iron deficiency, CKD, pregnancy, haemoglobinopathies).
What is the Estimated average glucose from HbA1c?
Estimated average glucose (eAG) translates HbA1c into the average glucose level it reflects over about 3 months. The ADAG study (Nathan et al., Diabetes Care 2008) derived the linear relationship from frequent glucose measurements in 507 people with type 1, type 2 or no diabetes at 10 international centres.
When to use it
- Explaining HbA1c to patients in the same units as their meter readings (mmol/L)
- Comparing HbA1c with self-monitoring or CGM averages
- Converting IFCC mmol/mol values from European laboratories
When not to use it
- Conditions with altered red-cell lifespan (haemolysis, recent transfusion, iron deficiency, advanced CKD)
- Pregnancy and haemoglobinopathies
How it is calculated
eAG (mmol/L) = 1.59 × HbA1c (%) − 2.59; HbA1c (%) = 0.0915 × HbA1c (mmol/mol) + 2.15.
Clinical pearls and limitations
- Population average: the SD of the prediction error was 0.87 mmol/L, and HbA1c is misleading with altered red-cell lifespan (haemolysis, iron deficiency, CKD, pregnancy, haemoglobinopathies).
- HbA1c 7 % (53 mmol/mol) corresponds to an average glucose of about 8.5 mmol/L (154 mg/dL).
- Individual eAG varies: the prediction error SD was 0.87 mmol/L.
- European laboratories report HbA1c in IFCC mmol/mol; % = 0.0915 × mmol/mol + 2.15.
Frequently asked questions
How do I convert HbA1c to average glucose in mmol/L?
eAG (mmol/L) = 1.59 × HbA1c (%) − 2.59. For mmol/mol, first convert to % with 0.0915 × mmol/mol + 2.15.
What average glucose is an HbA1c of 48 mmol/mol?
48 mmol/mol is 6.5 %, which corresponds to about 7.8 mmol/L.
Why does my CGM average differ from the eAG?
Red-cell lifespan and glycation rates vary between individuals; CGM-derived glucose management indicator (GMI) and eAG are related but not identical.
Evidence and guidelines
- Primary source: Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ; ADAG Study Group. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31(8):1473-1478.
- Hoelzel W et al. IFCC reference system for measurement of hemoglobin A1c in human blood and the national standardization schemes in the United States, Japan, and Sweden. Clin Chem 2004;50(1):166-174 (NGSP = 0.915 × IFCC[%] + 2.15).
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<p><a href="https://medelix.ai/en/calculators/hba1c-estimated-average-glucose">Estimated average glucose from HbA1c calculator by Medelix</a></p>For healthcare professionals and medical students. These tools support, and do not replace, clinical judgement. Always check results against the original source and your local protocols.