How Diabetes is Diagnosed

Diabetes is diagnosed with a blood test that measures the amount of glucose, or sugar, in your blood. There are two basic blood sugar tests:

Fasting Plasma Glucose (FPG)

The easiest way to diagnose diabetes is to measure your fasting plasma glucose (FPG) — that is, the amount of sugar in your blood after you haven't eaten for several hours. For this blood sugar test, you have to fast (not eat or drink anything except water) for at least 8 hours before having your blood drawn. The test is usually performed in the morning.

If your FPG value is 126 mg/dl or more, the test is repeated on a different day. An FPG value of 126 mg/dl or more on two different days means that you have diabetes.

Oral Glucose Tolerance Test (OGTT)

Another blood sugar test that may be used to diagnose diabetes is called the oral glucose tolerance test. For this test, your blood sugar is measured 2 hours after you drink a special high-sugar drink. If your blood sugar value is 200 mg/dl or more on 2 different days, that means you have diabetes.

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