Testing for diabetes

How is diabetes diagnosed?

The fasting blood glucose test is the preferred test for diagnosing diabetes in children and non-pregnant adults. It is most reliable when done in the morning. However, a diagnosis of diabetes can be made based on any of the following test results, confirmed by retesting on a different day:

A blood glucose level of 126 milligrams per deciliter (mg/dL) or more after an eight-hour fast. This test is called the fasting blood glucose test.
A blood glucose level of 200 mg/dL or more two hours after drinking a beverage containing 75 grams of glucose dissolved in water. This test is called the oral glucose tolerance test (OGTT).
A random (taken at any time of day) blood glucose level of 200 mg/dL or more, along with the presence of diabetes symptoms.

What is pre-diabetes?

People with pre-diabetes have blood glucose levels that are higher than normal but not high enough for a diagnosis of diabetes. This condition raises the risk of developing type 2 diabetes, heart disease, and stroke.

Pre-diabetes is also called impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), depending on the test used to diagnose it. Some people have both IFG and IGT.

IFG is a condition in which the blood glucose level is high (100 to 125 mg/dL) after an overnight fast, but is not high enough to be classified as diabetes. (The former definition of IFG was 110 mg/dL to 125 mg/dL.)
IGT is a condition in which the blood glucose level is high (140 to 199 mg/dL) after a two-hour oral glucose tolerance test, but is not high enough to be classified as diabetes.

Testing for diabetes

How is diabetes diagnosed?

What is pre-diabetes?

People with pre-diabetes have blood glucose levels that are higher than normal but not high enough for a diagnosis of diabetes. This condition raises the risk of developing type 2 diabetes, heart disease, and stroke.

Pre-diabetes is also called impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), depending on the test used to diagnose it. Some people have both IFG and IGT.

IFG is a condition in which the blood glucose level is high (100 to 125 mg/dL) after an overnight fast, but is not high enough to be classified as diabetes. (The former definition of IFG was 110 mg/dL to 125 mg/dL.)

IGT is a condition in which the blood glucose level is high (140 to 199 mg/dL) after a two-hour oral glucose tolerance test, but is not high enough to be classified as diabetes.