Tests To Detect Diabetes

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Tests To Detect Diabetes

Diabetes Type 2
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Tests To Detect Diabetes
Tests To Detect Diabetes
Learn how to find out if you have diabetes.
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Reviewed by the Faculty of Harvard Medical School

Tests To Detect Diabetes
A variety of blood tests can diagnose diabetes. Some tests directly measure your blood sugar (glucose). Another test shows the effect of blood sugar levels on hemoglobin proteins in the blood. This is called the A1C test.
There are four ways that your tests can fit a diagnosis of diabetes:
  1. Hemoglobin A1C test — Diabetes is diagnosed if your blood A1C is at least 6.5%. Test results between 5.7% and 6.4% do not diagnose diabetes. But they suggest that your risk for diabetes is high. You don't have to avoid eating right before an A1C test. This test is not accurate for people with anemia, people whose spleen has been removed or pregnant women.
  2. Fasting plasma glucose test — You don't eat and don't drink anything but water for 8 hours before the test. Diabetes is diagnosed by a glucose level of at least 126 milligrams per deciliter (mg/dl).
  3. Random plasma glucose test — This test can be used if you have symptoms that suggest diabetes. To diagnose diabetes with symptoms, your glucose with or without eating must be at least 200 mg/dl.
  4. Oral glucose tolerance test — Your doctor gives you a 75-gram sugar drink. Your blood glucose is measured two hours after you drink it. Diabetes is diagnosed if your glucose is at least 200 mg/dl.

A woman who is pregnant can be diagnosed with a special form of diabetes called gestational diabetes. The cutoffs for diagnosing this form of diabetes are different. That's because glucose levels usually are lower during pregnancy.

Generally, you have to have blood tests on two separate days to be diagnosed with diabetes. Both tests must fit the criteria above.
Your doctor usually can tell you the type of diabetes that you have based on your medical history, family history and a physical examination. Most people diagnosed as adults (except during pregnancy) have type 2 diabetes.
If your glucose or A1C level is above normal but not high enough for a diagnosis of diabetes, you may have pre-diabetes. A glucose level in this range does not usually cause sugar-related symptoms, such as frequent urination, extra thirst or blurred vision. It does increase the chance that you will eventually develop diabetes. Even before diabetes develops, high blood sugar increases your risk of long-term complications.
Don't be confused! The numbers that are used for diagnosing diabetes are different than the numbers that are used as goals for treatment in diabetes.


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Last updated October 28, 2013

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