What is Oral Glucose Challenge Test?
It is a test that measures the body’s response to sugar.
Why do you need to take this test?
Glucose is the sugar the body uses for energy. People with untreated diabetes have high blood glucose levels.
Most often, the first tests used to diagnose diabetes in people who are not pregnant are:
- Fasting blood glucose level: diabetes is diagnosed if it is higher than 126 mg/dL (7 mmol/L) on 2 different tests
- Hemoglobin A1c test: diabetes is diagnosed if the test result is 6.5% or higher
Glucose tolerance tests are also used to diagnose diabetes. The OGTT is used to screen for or diagnose diabetes in people with a fasting blood glucose level that is high, but is not high enough (above 125 mg/dL or 7 mmol/L) to meet the diagnosis for diabetes.
Abnormal glucose tolerance (blood sugar goes too high during the glucose challenge) is an earlier sign of diabetes than an abnormal fasting glucose.
- Make sure you eat normally for several days before the test.
- DO NOT eat or drink anything for at least 8 hours before the test. You cannot eat during the test.
- Ask your health care provider if any of the medicines you take can affect the test results.
Normal blood values for a 75 gram OGTT used to check for type 2 diabetes in those who are not pregnant:
- Fasting: 60 to 100 mg/dL (3.3 to 5.5 mmol/L)
- 1 hour: less than 200 mg/dL (11.1 mmol/L)
- 2 hours: less than 140 mg/dL (7.8 mmol/L)
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
A glucose level that is higher than normal may mean you have pre-diabetes or diabetes:
- A 2 hour value between 140 and 200 mg/dL (7.8 and 11.1 mmol/L) is called impaired glucose tolerance. Your doctor may call this “pre-diabetes.” It means you are at increased risk of developing diabetes over time.
- A glucose level of 200 mg/dL (11.1 mmol/L) or higher is used to diagnose diabetes.
Serious stress to the body, such as from trauma, stroke, heart attack, or surgery, can raise your blood glucose level. Vigorous exercise can lower your blood glucose level.
Any questions? Please don’t hesitate to contact us. We will do our best to help you.