Monitoring glucose levels involves daily checks or continuous monitors for immediate readings. While these are helpful for adjustments, the HbA1c test offers a broader, long-term perspective on glucose control. Since the HbA1c result is reported as a percentage, it is often difficult for people to relate it to the familiar units they see on their home meters. Estimated Average Glucose (EAG) was developed to bridge this gap, translating the long-term percentage into a unit directly comparable to daily blood sugar numbers.
What Is Estimated Average Glucose (EAG)?
Estimated Average Glucose (EAG) is a calculated value that represents a person’s average blood sugar level over a period of approximately two to three months. It is not a direct measurement of glucose but rather an estimate derived from the long-term HbA1c blood test. The concept was established by the American Diabetes Association (ADA) and other professional organizations to make the results of the HbA1c test more understandable for patients.
The purpose of EAG is to translate the percentage-based HbA1c result into the units used by home monitors: milligrams per deciliter (mg/dL) in the United States or millimoles per liter (mmol/L) internationally. This translation helps patients visualize their long-term glucose control in familiar terms. EAG encourages a better understanding of how well diabetes is being managed over the preceding two to three months.
The Conversion: Understanding the Link Between EAG and A1c
The HbA1c test measures the percentage of hemoglobin, a protein in red blood cells, that has glucose attached to it, a process known as glycation. Since red blood cells have a lifespan of around three months, the HbA1c percentage reflects the average glucose concentration the cells were exposed to during that time. A higher HbA1c percentage means a higher average amount of glucose has been stuck to the hemoglobin.
The EAG value is the direct mathematical translation of the HbA1c percentage into a standard blood glucose unit. This linear correlation was established through extensive research, most notably the A1c-Derived Average Glucose (ADAG) study. The formula used to calculate EAG is eAG = (28.7 x A1c) – 46.7 when the result is expressed in mg/dL.
For example, an A1c of 7.0% corresponds to an EAG of 154 mg/dL. The following table shows the correspondence between common A1c results and their estimated average glucose equivalents in both units of measure:
| A1c (%) | EAG (mg/dL) | EAG (mmol/L) |
| :—: | :—: | :—: |
| 6.0 | 126 | 7.0 |
| 7.0 | 154 | 8.6 |
| 8.0 | 183 | 10.1 |
This direct conversion allows patients to easily compare their long-term control, expressed as EAG, with the instantaneous readings from their home glucose meter. The closer the EAG is to the desired average, the better the overall glucose management has been over the past few months.
How to Interpret and Use Your EAG Numbers
EAG is a tool for assessing the overall effectiveness of your diabetes treatment plan, including medication, diet, and lifestyle choices. It offers a comprehensive view that cannot be achieved with single, daily finger-stick measurements alone. By looking at the EAG, you and your healthcare provider can determine if adjustments are needed to improve long-term control.
The target EAG range is individualized, but generally, an EAG below 114 mg/dL aligns with a non-diabetic A1c level. For most non-pregnant adults with diabetes, the American Diabetes Association recommends a goal A1c of less than 7%, which translates to an EAG of less than 154 mg/dL. Maintaining an EAG within this target range helps to significantly lower the risk of developing long-term diabetes complications.
The EAG is an average, reflecting a mix of high and low glucose readings over three months. A patient’s average of self-monitored readings might differ slightly from their EAG because people often check levels at specific times, rather than constantly throughout the day. Using the EAG alongside daily glucose logs provides a valuable, comprehensive picture of blood sugar control and progress.
A high EAG indicates that average blood glucose levels have been elevated over the past few months, signaling that the current management strategy may not be working effectively. Conversely, an EAG within the target shows that lifestyle and medication changes are having a positive long-term effect. Discussing this number with your doctor is an opportunity to refine your personal treatment goals and make proactive changes.