What is the hemoglobin A1c test

Date: Aug-29-2013The hemoglobin A1c test is a common blood test used to determine how well patients are managing their diabetes. It is also called the HbA1c, glycohemoglobin, or glycated hemoglobin test. The test is commonly used to screen for type 1 and 2 diabetes.

The HbA1c test shows the patient's average blood sugar levels for the past two or three months. It measures how much of the hemoglobin is glycated (coated in sugar).

Hemoglobin is a protein-based substance within red blood cells that carries oxygen from the lungs to the rest of the body. Glucose enters the red blood cells and glycates (links up) with hemoglobin molecules. If there is a lot of glucose in your blood, more hemoglobin gets glycated.

The average amount of glucose in the blood can be tested by measuring the hemoglobin A1c level. If glucose levels have been high over the last two to three months, the A1c test will reflect that with a high reading.

A high A1C level test result means there is poor blood sugar control. Poor blood glucose control increases the risk of diabetes complications.

According to the National Institutes of Health, the following are the most common complications for diabetes patients with poor blood sugar control:

Heart disease
Eye disease
Kidney disease
Stroke
Nerve damage

Researchers at the Johns Hopkins Bloomberg School of Public Health reported in NEJM that measurements of HbA1c predict a person's risk of complications more accurately than the commonly used measurement of fasting glucose.
What is a normal HbA1c reading?

HbA1c test results are interpreted as follows:

Between 4% and 5.6% - the person is healthy and at minimum risk of diabetes
Between 5.7% and 6.4% - the person has a higher risk of diabetes
6.5% or more - the person has diabetes

Patients with anemia, those taking some vitamin supplements (vit C and E), patients with high blood cholesterol levels, and people with liver or kidney diseases may have abnormal HA1c test results. If you are taking supplements, tell your doctor.

People who poorly control their diabetes - those who have high HA1c test scores - have a much higher risk of developing complications.

The American Diabetes Association suggests a maximum A1c of 7% for patients with diabetes.
How often should I have the HA1c test?

If you have diabetes, you should do the hemoglobin A1c test every quarter to make sure that your level does not exceed 7%.

If you have diabetes and have had good blood sugar control for a while, your doctor may recommend checking once every six months.
What is the difference between A1c and eAG?

Some health care providers may report an A1c result as eAG (average glucose). eAG directly correlates to A1c.

A1c is reported as a percent, e.g. 7%
eAG is reported as mg/dl (milligrams per deciliter), as the glucose meters, e.g. 154 ml/dl
A1c of 5 = 97 eAG, A1c of 6 = 126 eAG, A1c of 7 = 154 eAG, A1c of 8 = 183 eAG, A1c of 9 = 212 eAG

A study published in The Lancet in 2010 suggested that low HbA1c levels may be as dangerous as high levels in diabetes patients regarding mortality and cardiovascular disease risk. After reviewing the study, The Endocrine Society recommended against any wholesale change in glycemic goals.
A1C test for diabetes, prediabetes - NIH

This video shows NIH Clinical Center staff members working with medical samples in a laboratory setting to complete tests. NIH Clinical Center's Dr. David Sacks is interviewed.

Written by Christian Nordqvist

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