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eAG: Turning Your A1C Into Everyday Glucose Numbers
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What is it?
Estimated Average Glucose (eAG) is a number that shows your average blood sugar over the past 3 months, based on your hemoglobin A1C (HbA1c) test result. It helps connect long-term lab values like A1C with day-to-day blood sugar levels—such as those from a finger-prick test or continuous glucose monitor (CGM).
Why it matters
By translating A1C into the same units as daily glucose readings (mg/dL or mmol/L), eAG makes it easier to understand how your fasting blood sugar or CGM trends relate to your overall glucose control. This helps you and your care team make more informed decisions based on both short-term and long-term data.
The American Diabetes Association supports using eAG to help people talk about and track their glucose levels.
A1C remains the main test used to diagnose and monitor diabetes.
Reference ranges
There are no established reference ranges for eAG. However, given that eAG is directly derived from A1C, it is reasonable to set references for eAG to correspond with current A1C reference ranges.
It is important to recognize that the eAG is an estimate, based on a single measure of long-term blood glucose control (A1C). The conversion from A1C to eAG assumes a linear relationship, which might not always accurately reflect glucose variability or postprandial spikes, potentially leading to misinterpretation of glucose control. Significant variation may exist between eAG and actual mean (or average) glucose determined via continuous glucose monitoring or frequent glucometer tests (Chalew, Hempe, & McCarter, 2009). Clinical decision-making should be based on a combination of A1C and glucose self-monitoring results, rather than eAG.
American Diabetes Association. (n.d.). Estimated average glucose: An alternative to A1C. Retrieved from https://www.diabetes.org
Chalew, S. A., Hempe, J. M., & McCarter, R. (2009). Clinically significant disagreement between mean blood glucose and estimated average glucose in two populations: Implications for diabetes management. Journal of Diabetes Science and Technology, 3(5), 1128–1135. https://doi.org/10.1177/193229680900300516
Dib, J. G. (2010). Estimated average glucose: A new term in diabetes control. Annals of Saudi Medicine, 30(1), 85. https://doi.org/10.4103/0256-4947.59375
Nathan, D. M., Kuenen, J., Borg, R., Zheng, H., Schoenfeld, D., Heine, R. J., & A1c-Derived Average Glucose Study Group. (2008). Translating the A1C assay into estimated average glucose values. Diabetes Care, 31(8), 1473–1478. https://doi.org/10.2337/dc08-0545
National Glycohemoglobin Standardization Program. (n.d.). A1C-derived average glucose (eAG). Retrieved from https://ngsp.org/A1ceAG.asp
Brick, J. C., Derr, R. L., & Saudek, C. D. (2009). A randomized comparison of the terms estimated average glucose versus hemoglobin A1C. The Diabetes Educator, 35(4), 596–602. https://doi.org/10.1177/0145721709336298
Sacks, D. B., Arnold, M., Bakris, G. L., Bruns, D. E., Horvath, A. R., Lernmark, Å., Metzger, B. E., Nathan, D. M., & Kirkman, M. S. (2023). Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Diabetes Care, 46(10), e151–e199. https://doi.org/10.2337/dci23-0036
This information is educational and does not replace medical advice, diagnosis, or treatment. Your results should be interpreted with a qualified healthcare professional in the context of your health history.
