Estimated Average Glucose From HbA1c
Converts HbA1c into estimated average glucose in mg/dL and mmol/L using the ADAG study equation.
When to use
Adults with diabetes and HbA1c measured by a standardized assay, to translate the result into average glucose.
Pearls and pitfalls
- The equation estimates the population average; an individual mean glucose can differ, with an SD of prediction error of 15.7 mg/dL.
- Anemia, altered erythrocyte turnover and hemoglobinopathies change HbA1c and make the estimate unreliable.
- Children and pregnant women were excluded from the ADAG study; the relationship in these groups is not established.
- The published table covers HbA1c from 5% to 12%, and 98.5% of the sample was between 4% and 10%; values outside that range are extrapolation.
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Formula
eAG (mg/dL) = 28.7 × HbA1c (%) − 46.7. eAG (mmol/L) = 1.5944 × HbA1c (%) − 2.594.
Evidence
Linear regression in 507 participants, 268 with type 1 diabetes, 159 with type 2 and 80 without diabetes, with about 2,700 glucose values per participant over 3 months; R² = 0.84.
References
- Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008;31(8):1473-1478. doi:10.2337/dc08-0545
Frequently asked questions
What is Estimated Average Glucose From HbA1c?
Converts HbA1c into estimated average glucose in mg/dL and mmol/L using the ADAG study equation. Adults with diabetes and HbA1c measured by a standardized assay, to translate the result into average glucose.
How is the result calculated?
eAG (mg/dL) = 28.7 × HbA1c (%) − 46.7. eAG (mmol/L) = 1.5944 × HbA1c (%) − 2.594.
How should the result be interpreted?
Linear regression in 507 participants, 268 with type 1 diabetes, 159 with type 2 and 80 without diabetes, with about 2,700 glucose values per participant over 3 months; R² = 0.84.
What are the sources?
Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008;31(8):1473-1478.