New guidelines released from the American Diabetes Association (ADA) this month feature a larger role for the hemoglobin A1C blood test. The simple test, which measures average blood sugar levels for the previous two to three months, has long been used to help manage diabetes. But now it can be used to diagnose type 2 diabetes and prediabetes too.
Other methods for diagnosing diabetes are still valid. But the A1C test offers greater convenience because no fasting is required. The test measures the amount of hemoglobin, a substance in the blood, that has a blood sugar molecule attached to it. This happens when blood sugar levels are too high.
The guidelines, which appear in the journal Diabetes Care, state that an A1C level above 6.5 percent indicates type 2 diabetes. Levels between 5.7 and 6.4 percent indicate prediabetes. Most people without diabetes have an A1C level less than 5 percent.
In the past, A1C was not recommended to diagnose diabetes because the test was not standardized across labs. But today it is. This means that two different labs testing the same blood should provide the same results.
Any of the following blood tests can be used to diagnose diabetes:
An A1C test can be performed at any time of day, without fasting.
A fasting blood glucose test is usually done in the morning, after fasting for at least eight hours.
An oral glucose tolerance test also requires fasting for at least eight hours. However, after the fast you drink a beverage that contains glucose. Two hours later, your blood sugar levels are measured.
A random plasma glucose test can be done at any time. It is performed mainly in people who already have diabetes symptoms, such as increased urination, thirst, or unexplained weight loss.
If test results indicate that you have diabetes, a second test should be performed on a different day to be sure.
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According to the ADA, adults of all ages should talk with their doctors about getting tested for diabetes if they are overweight or obese and they have one or more risk factors for diabetes, some of which include:
The ADA recommends that adults who are not overweight should consider getting tested at least every three years starting at age 45.
Always consult your physician for more information.