What is Estimated Average Glucose (eAG)?
Estimated Average Glucose (eAG) is a calculated value derived from HbA1c that translates the percentage-based HbA1c result into the same glucose units (mg/dL or mmol/L) used in daily blood glucose monitoring, making it easier for patients to understand their average blood glucose levels over the preceding 2-3 months. 1
Mathematical Relationship and Calculation
eAG is calculated using the regression equation established by the international A1C-Derived Average Glucose (ADAG) study: eAG (mg/dL) = 28.7 × HbA1c (%) - 46.7, with a strong correlation coefficient of r = 0.92 between HbA1c and mean glucose. 1, 2
The ADAG study analyzed approximately 2,700 glucose measurements over 3 months per HbA1c measurement in 507 adults with type 1 diabetes, type 2 diabetes, and no diabetes. 1
A calculator for converting A1C results into eAG is available at professional.diabetes.org/eAG. 1
Standard Conversion Table
The following table shows the correlation between HbA1c percentages and eAG values 1:
| HbA1c (%) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 5 | 97 (76-120) | 5.4 (4.2-6.7) |
| 6 | 126 (100-152) | 7.0 (5.5-8.5) |
| 7 | 154 (123-185) | 8.6 (6.8-10.3) |
| 8 | 183 (147-217) | 10.2 (8.1-12.1) |
| 9 | 212 (170-249) | 11.8 (9.4-13.9) |
| 10 | 240 (193-282) | 13.4 (10.7-15.7) |
Values in parentheses represent 95% confidence intervals
Clinical Purpose and Utility
eAG uses the same measurement units (mg/dL or mmol/L) that patients see on their glucose meters and lab reports, making HbA1c results more intuitive and easier to understand. 1
The American Diabetes Association and the American Association for Clinical Chemistry determined that the correlation in the ADAG trial is strong enough to justify reporting both the A1C result and the eAG result when a clinician orders the A1C test. 1
eAG provides patients with an estimate of their average blood glucose over a period of time, helping them understand the effectiveness of their treatment regimen. 1
Critical Limitations and When NOT to Use eAG
eAG reflects only average glucose levels and provides no information about glycemic variability, hypoglycemia risk, or extreme blood glucose readings. 1
Conditions That Invalidate eAG Accuracy:
Conditions affecting red blood cell turnover make eAG unreliable: hemolytic anemia, other anemias, glucose-6-phosphate dehydrogenase deficiency, recent blood transfusion, use of erythropoiesis-stimulating drugs, end-stage kidney disease, and pregnancy. 1
Hemoglobin variants can interfere with HbA1c measurement, though most U.S. assays are accurate in individuals heterozygous for common variants. 1
eAG cannot be measured in individuals with sickle cell disease (HbSS) or other homozygous hemoglobin variants since these individuals lack HbA. 1
Important Clinical Caveats
eAG should never be used to assess short-term diabetes complications or predict hypoglycemia risk, as it only reflects averages and cannot identify severe extreme blood glucose readings. 1
eAG has no value in employment evaluations or safety assessments for individuals with diabetes, as it provides no information about whether the person is at significant risk for hypoglycemia or suboptimal performance. 1
The ADAG study population was 83% non-Hispanic White, which limits generalizability to other ethnic populations. 1
There was a trend toward higher A1C values in African/African American individuals compared with non-Hispanic White individuals for a given mean glucose, though the study was underpowered to detect definitive differences. 1