What is A1C and How Do You Convert it to eAG?

Detailed info About These Two Common Terms

Picture of diabetes screening
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When you have diabetes, you will be asked to get a hemoglobin A1C (hbA1c) test. An A1C test is a test that provides information about a person's average glucose levels (provided as a percentage) over the course of two to three months. Depending on your diabetes control, insurance and treatment method, you maybe asked to get this test every six months or as often as every three months. Your A1C goal will also depend on various factors, such as your age, length of diagnosis, type of medication, type of diabetes, etc.

In addition to providing an idea of your level of control, these results can be used to tell if changes to your regimen have been beneficial and also give an idea of risks for complications. The result can also help guide your physicians making changes to your medication regimen or provide advice on how to make lifestyle changes, such as diet and exercise which can help to improve your diabetes control. Your A1C is not a measure of a single blood glucose, rather an overall picture of your diabetes control. Your A1C is measured as a percentage.

The A1C is different than eAG. eAG, otherwise known as estimated average glucose, is a measure of your average blood glucose over the course of two to three months in mg/dL. Your A1C is directly correlated to your eAG which can help you to have a better understanding of your diabetes control. 

Sometimes the A1C number can be confusing, especially when you are not sure what the percentage translates to.

When you are testing your blood sugars daily, the numbers you see on your monitor are also measured in mg/dL. But, these numbers reflect a moment in time and are not the same as your eAG. It is important to test your blood sugar daily to help you to pattern manage and prevent high and low blood sugars, but if you are looking to understand how your control is over time you can use the A1C or eAG.


You can learn how the A1C is translated into estimated average blood sugars by reading this chart:

A1c to eAG Conversion Chart

HbA1c or A1ceAG

The formula is used is: 28.7 X A1C - 46.7 = eAG

The eAG translates the A1C test result into units patients are more familiar with when testing at home.

How is it Calculated?

Glucose enters your red blood cells and attaches to (or glycates)  hemoglobin. Every three months or so these cells die and get replenished. A blood test or A1C test, provides results regarding how much sugar has attached to your red blood cells over the course of two to three months. According to the American Diabetes Association, most adults should aim for an A1C of 7% or lower (without having low blood sugars). For more information on what your blood sugars should be read: A1C and Blood Sugar Goals 

An A1c test also can be used to diagnose diabetes. Any adult with an A1C of 6.5% or above is considered to have diabetes.

And any adult with an A1C of 5.7%-6.4% is considered to have prediabetes. Although A1C is one way to diagnose diabetes and prediabetes, the American Diabetes Association states that no one method is considered better than another. The American Diabetes Association also states: "it is important to take age, race/ethnicity, and anemia/hemoglobinopathies into consideration when using A1C to diagnose diabetes."

Updated on May 27, 2016 by: Barbie Cervoni MS, RD, CDE


A1C. American Diabetes Association. Accessed: April 20, 2011. http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/a1c

Nathan MD, David M; Kuenen MD, Judith; Borg MD, Rikke; Zheng PHD, Hui; Schoenfeld PHD, David; Heine MD, Robert J for the A1c-Derived Average Glucose (ADAG) Study Group. "Translating the A1c Assay Into Estimated Average Glucose Values." Diabetes Care Aug 2008 31(8):1473-1478

National Institute of Diabetes and Digestive and Kidney Diseases. What is the A1C Test? Accessed on-line. May 27, 2016: http://www.niddk.nih.gov/health-information/health-topics/diagnostic-tests/a1c-test-diabetes/Pages/index.aspx#1

American Diabetes Association. Standards of Medical Care in Diabetes – 2016. Diabetes Care. 2016 Jan; 39 (Suppl 1): S1-109.

Amercian Diabetes Assocication. A1c and eAG. Accessed on-line. May 24, 2016: http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/a1c/?referrer=https://www.google.com/

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