Estimated Average Glucose (eAG)

Estimates mean plasma glucose from HbA1c using the ADAG formula validated by the American Diabetes Association.

Endocrinology EndocrinologyEvidence-BasedUpdated 2026-08-06

Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.

Clinical Notes

Estimated average glucose (eAG) is derived from the ADAG study equation relating glycated hemoglobin to average glucose: eAG (mg/dL) = 28.7 × HbA1c − 46.7. HbA1c reflects average glycemia over the preceding 2–3 months, and eAG translates it into the mg/dL units that patients see on home glucose meters. An eAG value is a statistical estimate based on a studied population, not a direct glucose measurement, and it corresponds imperfectly to finger-stick or meter averages in any individual. It also does not convey glucose variability or the occurrence of hypoglycemic episodes. HbA1c-derived estimates assume normal red blood cell survival and unaltered hemoglobin. Hemoglobin variants, anemia, and any condition that shortens or lengthens red cell lifespan (e.g., hemolysis, recent transfusion, iron deficiency) can distort HbA1c and therefore eAG. For this reason, eAG should be interpreted alongside self-monitored glucose (SMBG) or continuous glucose monitoring (CGM) data and the full clinical context whenever possible.

Calculator Information

Specialty

Endocrinology

📋 Reference Ranges

Normal Range

70–140 mg/dL

Reference ranges for this calculator
Classification	Range
Normal average glucose	<140.1
Pre-diabetic range	140–200
Diabetic range	≥200

What This Calculator Measures

Estimates mean plasma glucose from HbA1c using the ADAG equation, translating A1c into a mg/dL value patients can compare with home glucose readings.

How to Use

Enter the NGSP-standardized HbA1c value (%).
Review the estimated average glucose in mg/dL.
Interpret against the normal range of 70–140 mg/dL and the ADA target of eAG ≈154 mg/dL.

How the Calculation Works

Estimated average glucose (mg/dL) = 28.7 x HbA1c (%) - 46.7, the ADAG equation relating HbA1c to mean plasma glucose.

Variables Explained

HbA1c

Glycated hemoglobin in percent, multiplied by 28.7 and reduced by 46.7 to estimate average glucose.

Interpretation Guide

eAG ≤140 mg/dL is normal, eAG above 140 up to 200 mg/dL is the pre-diabetic range, and eAG >200 mg/dL is in the diabetic range. eAG reflects average glucose over the preceding 2–3 months.

Clinical Significance

eAG converts A1c into a practical mg/dL value, improving patient comprehension and facilitating shared decision-making about glycemic control.

When It Is Useful

Translating A1c into familiar glucose units for patient education
Assessing overall glycemic control over 2–3 months
Setting and reviewing glycemic targets

When It Is Not Useful

In conditions altering red cell lifespan (iron deficiency, sickle cell trait, pregnancy)
As a substitute for CGM or self-monitoring data when variability is the question

Common Mistakes

Trusting eAG in a patient with sickle cell trait or recent transfusion, conditions that alter red cell lifespan and distort the A1c feeding the equation.
Using eAG to judge hypoglycemia risk or day-to-day variability, questions that call for self-monitored or continuous glucose data instead.
Expecting eAG to reproduce a personal meter average exactly, since it was derived from continuous glucose monitoring studies as a population estimate.

Limitations

Derived from continuous glucose monitoring studies and may differ from finger-stick averages.
Does not reflect glucose variability or hypoglycemic episodes.
Affected by conditions that change red blood cell survival.

Worked Example

A 60-year-old patient with impaired glucose tolerance has an HbA1c of 6.0%.

Inputs:

a1c: 6.0

Expected Result: eAG = 28.7 × 6.0 − 46.7 = 125.5 mg/dL — normal average glucose range.

Evidence & References

Source:: ADA / ADAG Study
Reference:: Nathan DM, et al. Diabetes Care. 2008;31(8):1473-1478.

References

Nathan DM, Kuenen J, Borg R, et al. Translating the A1c assay into estimated average glucose values. Diabetes Care. 2008;31(8):1473-1478. (Primary Study)

Frequently Asked Questions

What is estimated average glucose?

eAG converts HbA1c into the estimated average blood glucose in mg/dL over the preceding 2–3 months, making it easier for patients to relate A1c to home glucose readings.

What A1c corresponds to an eAG of 126 mg/dL?

An eAG of 126 mg/dL corresponds to an HbA1c of approximately 6.0% using the ADAG formula.

Disclaimer: This calculator is intended for educational and clinical decision support purposes only. Use NGSP-standardized A1c values and interpret within the clinical context.