Managing long-term blood sugar levels is central to the care of individuals with diabetes. Healthcare providers use the Hemoglobin A1c (HbA1c) test as the standard clinical measurement to assess this control over two to three months. Since the HbA1c result is given as a percentage, it can seem abstract to patients. The Estimated Average Glucose (eAG) was developed to translate this complex clinical number into a more familiar and relatable format. This metric helps bridge the gap between a laboratory result and the numbers a person sees on their home glucose monitor.
Defining Estimated Average Glucose
Estimated Average Glucose (eAG) represents an average of a person’s blood sugar levels over the preceding two to three months. Unlike a single finger-prick test, which gives a snapshot of glucose levels at a specific moment in time, the eAG provides a broader perspective on glycemic management. It is directly calculated from the HbA1c percentage result obtained from a blood test.
The primary purpose of reporting the eAG is to express the long-term average glucose concentration in the same units that patients use for their daily self-monitoring. In the United States, this unit is typically milligrams per deciliter (mg/dL), or millimoles per liter (mmol/L) in many other parts of the world. Converting the HbA1c percentage into these familiar units makes the clinical data more intuitive and actionable for the individual.
How eAG Relates to HbA1c
The eAG is mathematically derived from the HbA1c test result. The relationship between the two metrics is a direct, linear, and standardized one, established through extensive scientific research. This standardization effort was solidified by the international A1c-Derived Average Glucose (ADAG) study, published in 2008.
The ADAG study analyzed the relationship between HbA1c and average blood glucose levels gathered from continuous glucose monitoring and frequent finger-stick tests. This research provided a reliable conversion formula, ensuring that the eAG calculation is consistent across different clinical settings. The formula translates the HbA1c percentage into the average glucose concentration.
The standardized formula for calculating eAG in mg/dL is eAG = (28.7 x A1C) – 46.7. For example, an HbA1c result of 7% translates to an eAG of 154 mg/dL. The conversion allows for a simple cross-reference, helping people connect their long-term clinical result with the daily glucose readings they are accustomed to seeing.
| A1C (%) | eAG (mg/dL) |
| :—: | :—: |
| 6 | 126 |
| 7 | 154 |
| 8 | 183 |
Understanding Your eAG Results
The eAG number serves as a valuable tool for assessing the overall effectiveness of a person’s diabetes care plan. For most non-pregnant adults with diabetes, a common target for HbA1c is less than 7%, which corresponds to an eAG of less than 154 mg/dL. Maintaining an eAG within this range is associated with a reduced risk of long-term diabetes-related complications.
Specific eAG goals must be individualized based on a person’s age, the presence of other health conditions, and their history of severe low blood sugar events. For instance, some individuals who are older may have a more relaxed target, such as an eAG corresponding to an A1c of 7.5% or 8%. Conversely, some may aim for a stricter goal, corresponding to an A1c below 6.5%.
The eAG is a long-term average, meaning it does not reflect daily fluctuations or the immediate effects of a meal or exercise. It is possible for a person to have an acceptable eAG but still experience significant daily swings in blood sugar, including episodes of hypoglycemia or hyperglycemia. Using the eAG, alongside daily blood sugar logs, provides the most complete picture of glucose control. This metric is a key point of discussion with a healthcare provider to determine if adjustments to medication, diet, or physical activity are necessary.