What Is A1C – A1C Test Explained

Healthy living for diabetics requires proper management of their diabetes. In order to know how their diabetes treatment is going, the A1C blood test is used. The A1C test is considered to be the primary test used to diagnose prediabetes, type 1 diabetes and type 2 diabetes by an international committee of experts including the American Diabetes Association, the European Association for the Study of Diabetes and the International Diabetes Federation. It not only tests for prediabetes and diabetes but it also tells how well a person is managing their diabetes by providing their average blood glucose levels over the past two to three months.

The A1C is a blood test that measures what percentage of hemoglobin has sugar attached to it. Hemoglobin is a protein found in red blood cells; it is responsible for carrying oxygen from the lungs to cells. Red blood cells are constantly being replenished as their typical lifespan is about three months making the A1C test a good reflection of a person’s average blood glucose levels over the past three months. The higher the percentage of sugar being attached to hemoglobin denotes a higher blood glucose level.

When using the A1C test, the results are accurate within .5 percent meaning if an A1C test result is 5 percent, it can be within a range varying from 4.5 to 5.5 percent. When using the A1C test to diagnose diabetes, a reading of 6.5 percent or higher on two separate tests is indicative of diabetes. For someone that does not have their diabetes under control, the A1C levels can easily be above 8 percent. In most cases where a person is already diagnosed with diabetes, an A1C level of 7 percent is the common target goal to achieve.

A1C can also be measured as eAG which is the estimated average glucose. eAG is measured as mg/dl (miligrams / deciliter) in the US or mmol/l (milimols / liter) in other parts of the world. eAG readings are calculated from A1C in order to provide people with diabetes a reference as they relate it to their daily glucose monitoring levels. Below is a table that displays the relationship between A1C and eAG:

Comparison of A1C and eAG levels
A1C % eAG (mg/dl) eAG (mmol/l)
6% 126 7.0
6.5% 140 7.8
7% 154 8.6
7.5% 169 9.4
8% 183 10.1
8.5% 197 10.9
9% 212 11.8
9.5% 226 12.6
10% 240 13.4

The actual formula used to convert A1C to eAG is listed below:

28.7 * A1C – 46.7 = eAG mg/dl

Glucose Calculator

A1C Levels
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The A1C test serves as an important indicator regarding risks of complication caused by diabetes such as blindness, nerve damage and kidney disease. Keeping A1C levels closer to normal helps to reduce the risk of complications caused by diabetes; a higher A1C increase the likelihood of complications. The test also provides a point of reference as to how a diabetes treatment plan is working. The American Diabetes Association recommends that an A1C test be performed at least twice a year.

How has your eAG or A1C results helped your diabetes management? What were your results when you were first diagnosed with diabetes and what are your current readings?