How do you find out if you have diabetes?

The results of a Fasting Plasma Glucose Test or an Oral Glucose Tolerance Test can tell if you have pre-diabetes or diabetes. Your blood glucose (sugar) will be measured and analyzed with standard numbers for each test. Whichever test is used, two or more test results are needed on different days for a diagnosis.

The Fasting Plasma Glucose Test is the preferred test for Type 1 and Type 2 diabetes or pre-diabetes. You will fast overnight -- don't eat anything for at least eight hours. The next morning your doctor will draw blood from a vein and send your blood sample to a laboratory to test how much glucose (sugar) is in your blood. It is best to have this test done in the morning because afternoon results tend to be lower. Read the latest news about this test. Here's what the test results can mean:

  • A normal glucose level is 110 milligrams per deciliter (mg/dl) or below.
  • A pre-diabetes level is between 110 mg per dl and 125 mg per dl, sometimes called impaired fasting glucose(IFG). This range is between normal and having diabetes.
  • A diabetic level is 126 mg/dl or higher.

Fasting Plasma Glucose Test

An Oral Glucose Tolerance Test (OGTT) may be done by your doctor to test for Type 1 or Type 2 diabetes or gestational diabetes. After you don't eat for 8-12 hours, your doctor will test the sugar in your blood. Then you will drink a liquid rich in sugar (glucose) dissolved in water. Over the next few hours, your doctor will test the sugar in your blood again and check your numbers against standard numbers. Here's what the test results can mean:

  • A normal glucose level will be less than 140 mg/dl.
  • A pre-diabetes level is between 141 mg/dl and 199 mg/dl, sometimes called impaired glucose tolerance(IGT).
  • A diabetic level is 200 mg/dl or more.

Oral Glucose Tolerance Test

If you are a pregnant woman being tested for gestational diabetes, the liquid you must drink will have less sugar (glucose) dissolved in water. The standard result numbers are also different:

Before drinking, a normal glucose level is 95 mg/dl or below. More testing is needed if glucose level is 140 mg/dl or more one hour after drinking the glucose liquid.

What are normal blood sugar numbers?
Your blood sugar goes up after eating, but should return to the normal range in 1-2 hours.

  • Before meals: 80 to 120
  • Two hours after meals: 180 or less
  • At bedtime: 100 to 140

If you have diabetes, a good blood sugar range is between 70 and 150, but everyone is different. Check with your doctor to see what is best for you.

To learn more:

Diabetes Tests & Diagnosis
(National Diabetes Information Clearinghouse: NDIC)
Find out how diabetes is diagnosed.

next » How is diabetes treated?

Written by: Barbara Carlson, M.L.S.
Last Modified: Monday November 04, 2019 11:31 AM