Home › Biomarkers › Estimated average glucose
In a study of 507 people from 10 centres around the world, HbA1c and average blood sugar over the 3 months before were closely related.[1]
On this page you can read what estimated average glucose is, what the guidelines say about a value that is too low or too high, what affects your value and which values are best to look at alongside it.
Also called: eAG, average glucose from HbA1c. At the lab: not applicable.
Estimated average glucose is your HbA1c converted into an average blood sugar value. HbA1c tells you something about your blood sugar over a longer period. With this conversion, you see that value in the same unit as an ordinary blood sugar measurement, such as millimoles per litre.[1, 2]
This value is not measured separately, but calculated from your HbA1c. HbA1c is the part of your haemoglobin that has sugar attached to it. Researchers compared HbA1c with the average blood sugar over the three months before and found a fixed formula. That formula did not clearly differ by age, sex or smoking.[1, 2]
In children and young people too, researchers found a direct relationship between HbA1c and average blood sugar. There, blood sugar was measured with a sensor over several days in a row. This means average blood sugar can easily be calculated from HbA1c.[1, 2]
If you track your blood sugar every day, you often measure it yourself with a finger prick. That result is given in milligrams per decilitre or millimoles per litre. HbA1c comes as a percentage. Estimated average glucose makes it easy to put those two side by side.[1]
In the study, each participant's blood sugar was measured thousands of times, with sensors and finger pricks, spread over 3 months. This means the formula is based on a good picture of true average blood sugar.[1]
The researchers concluded that for most people with a condition affecting blood sugar regulation, HbA1c can be expressed as estimated average glucose.[1]
| Level | Can point to | Who it is for |
|---|---|---|
| Higher HbA1c[1] | a higher average blood sugar over the previous 3 months | people in the study, with and without a condition affecting blood sugar regulation |
| Lower HbA1c[1] | a lower average blood sugar over the previous 3 months | people in the study, with and without a condition affecting blood sugar regulation |
| Formula: AG (mg/dl) = 28.7 x A1C - 46.7[1] | the estimated average glucose at a given HbA1c value | the same regardless of age, sex, type of condition, ancestry and smoking habits |
Source: Nathan et al., 2008, a study of 507 people from 10 centres. The study gives no cut-off values, only the relationship between HbA1c and average blood sugar.[1]
The value is calculated directly from your HbA1c. So a higher estimated average glucose goes together with a higher HbA1c. That can point to a higher average blood sugar in the 3 months before the measurement. The study does not name a limit above which the value is too high.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
The value follows your HbA1c through the formula. If your HbA1c goes up or down, your estimated average glucose moves with it.[1]
In the study, HbA1c at the end of 3 months was compared with blood sugar over that whole period. So your blood sugar during the day and at night over those months counts.[1]
In 50 children, researchers looked at blood sugar in the 5 days before the HbA1c measurement, measured with a sensor. That short period was also linearly related to HbA1c.[2]
Estimated average glucose is included in BioProfile 87, 121 and 150.[3]
The BioProfile editorial team wrote this page on 30 October 2026 from the sources below, which we read on 30 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert is still reviewing this page; once that review is done, the expert's name and the date of the review will appear at the top. This page offers explanation, not a diagnosis. Discuss an abnormal value with your GP.
