OGTT (Oral Glucose Tolerance Test)
Definition
A test that shows how well the body moves sugar from the blood into the tissues. A fasting blood sample is drawn, a sugary liquid is given to drink, and a second blood sample is taken about two hours later.
Purpose
Shows how the body processes sugar; used to screen for gestational diabetes (pregnancy sugar).
Results
There are two test formats:
| Test | Is fasting required | Time of blood draw |
|---|---|---|
| Glucose challenge test | No | 1 hour after the sugary liquid |
| OGTT | Yes | Fasting + ~2 hours later |
| OGTT, in pregnancy | Yes | Every 30 minutes for 2 to 3 hours |
If sugar comes back high on the challenge test, the physician may order an OGTT.
Normal Values
Specific to the laboratory and the guideline used, check the range on your report.
Risks and Limitations
Not following the fasting requirement before the test invalidates the result. The sugary liquid can cause nausea in some people.