A1C & eAG

Submitted by Thiruvelan on Wed, 06/23/2010
A1C & eAG

What is eAG? Estimated average glucose is a simple way to understand A1C. It provides your approximate average blood-glucose level for the last three months.

What is eAG?

Estimated average glucose eAG is a comfortable way to relate your A1C result to that of glucose meter reading. 

A1C result is available in percentage. Thus, challenging to understand and relate it to the self-monitoring blood glucose level. Therefore healthcare professionals coin a new term called estimated average glucose eAG. It could give their patients A1C result in an easy to understand terms.

Estimated average glucose (eAG) help translate your A1C % result into mg/dl or mmol/l. This way, it relates to the daily glucose meter reading.

Is Hba1c an average of blood glucose levels?

The hba1c test is not an average of blood glucose levels. Still, it is logical to assume a high glucose level leads to more glycation and increased HbA1c.


  1. Fasting plasma glucose level underestimates A1C. That is, estimated A1C based on fasting BS is lower than actual A1C.
  2. Post breakfast glucose levels overestimate A1C. That is, estimated A1C based on post-breakfast BS is higher than actual A1C.
  3. Post lunch glucose level relates to A1C comparable to mean plasma glucose.

What does an eAG mean? A1C of 7% does not confirm that your blood sugar is steadily maintained at X mg/dl (or mmol/l) for past 2 to 3 months. If you tested your BS for every minute, hour, day, and night for past 2 to 3 months, then its average might be equal to eAG.

Know the limitation of A1C & eAG

No doubt, eAG & A1C provide useful information to gain an idea of how well or bad is your diabetes control.

Only less than 4.7% of glucose linked to RBCs in the hemoglobin of a non-diabetic population. Short-term hourly blood sugar elevations do not have a significant change in the A1C number. Only, long term high BS leads to a slow rate of glucose linked with hemoglobin and elevated A1C.

For diabetics, eAG and A1C are just a piece of the puzzle for your entire blood sugar level management.

Excellent eAG & A1C, not necessarily means you are in reasonable diabetes control. Even a superb eAG and a1c may be due to a combination of undesirable high and low blood sugars. Thus, aside from getting your A1C test, you need to track blood sugar. The combination of BS and A1C (eAG) data provides the best info to assess your diabetes control.

In most occasions, healthy eAG mean to reflect most of your blood sugar readings are normal.

Two popular estimated Average Glucose (eAG) studies

In April 2009, the College of American Pathologists survey collected info from 3,000 labs. 16.7% of them reported eAG; 28.8% used ADAG formula, 22.6% used DCCT formula, and balance used other methods.

There are many studies and methods to convert A1C to blood-glucose level. Two significant studies are Diabetes Control & Complications Trial (DCCT), and A1C Derived Average Glucose (ADAG). These two studies provide different formulas for eAG.

Dr. Richard K. Bernstein, the author of the popular book "Diabetes Solution." He is the first who succeed in the use of a low-carb diet for his type 1 diabetes control (with an A1C of 4.2 to 4.6). He recommends DCCT's formula to convert A1C to eAG. 

We provide two A1C charts (eAG); one based on DCCT A1C chart and another based on ADAG A1C chart. We request you to put your mind and find which one best suits you. However, we trust Dr. Richard K. Bernstein. Additionally, our website visitors have preferred DCCT over ADAG formula.

Why my average glucose reading (from glucometer) and eAG (from A1C) differ?

Blood glucose levels from preceding 30 days influence about 50% of the total HbA1c.

Most glucose monitors provide an average of all the past several weeks or months reading. In many instances, this meter average might not be the same as the eAG, learn why?

Your blood glucose meter provides blood glucose level at that moment. Even if you are testing ten or more times, then the average is likely to be higher or lower than your eAG. However, eAG is an average of glucose level 24/7 for lost two to three months.