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Diabetes Health Center

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A1C Blood Test OK for Diabetes Diagnosis

New Guidelines Call for Using A1C Blood Test to Identify People With Prediabetes
WebMD Health News

Dec. 29, 2009 -- The American Diabetes Association (ADA) is recommending that a simple blood test currently used to assess whether diabetes is under control also be used to diagnose the disease.

The blood test -- known as the A1C test -- has several important advantages over traditional blood glucose testing.

Patients do not need to fast before the test is given, and it is far less likely to identify clinically irrelevant fluctuations in blood sugar because it measures average blood glucose levels over several months.

The new guidelines do not call for replacing traditional screening with the A1C test.

It is believed that around 6 million Americans have diabetes but don't know it, and another 57 million have prediabetes.

The A1C test may help identify a large number of people in both of these groups, former ADA president for medicine and science John Buse, MD, PhD, tells WebMD.

Buse, who is chief of endocrinology at the University of North Carolina, Chapel Hill, helped draft the new ADA diabetes care guidelines, which were made public today.

"We now know that early diagnosis and treatment can have a huge impact on outcomes by preventing the complications commonly seen when diabetes is not well controlled," he says. "Our hope is that people with early or prediabetes who might otherwise not be tested would have the A1C test."

How the A1C Test Works

The A1C test has been used since the late 1970s as a measure of how well diabetes is managed, but the ADA had not previously recommended it for diagnosing the disease.

In part, this is because earlier versions of the test were not as accurate as current versions.

The test measures the percentage of glycated hemoglobin, or A1C, in the blood and provides an assessment of blood sugar levels over the previous two to three months.

Hemoglobin is a protein on red blood cells that carries oxygen in the blood. When blood sugar is too high it combines with hemoglobin.

The more excess glucose in the blood, the higher the percentage of A1C. Healthy adults without diabetes or prediabetes have an A1C of about 5%. Diabetes patients with very poorly controlled disease can have levels as high as 25%.

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