Key points about glucose tolerance test
- Measures how your body processes sugar over time
- Commonly used to diagnose diabetes or gestational diabetes
- Requires fasting before the test
- Involves drinking a sugary drink and having blood drawn several times
- Results help doctors understand how your body handles glucose
Overview
A glucose tolerance test checks how your blood sugar levels change after drinking a sugary liquid. It helps doctors detect problems with how your body uses insulin, the hormone that controls blood sugar. It’s most often used for diagnosing type 2 diabetes or gestational diabetes.
Candidates for glucose tolerance test
You may need this test if you:
- Show signs of diabetes, such as extreme thirst or fatigue
- Had an abnormal blood sugar result on another test
- Are pregnant and being screened for gestational diabetes
- Have risk factors for diabetes, like obesity or a family history
Preparation for glucose tolerance test
You’ll need to fast for 8–12 hours before the test—no food or drinks except water. Let your doctor know about any medications you’re taking, as some may affect your results.
Risks for glucose tolerance test
The test is generally safe. Possible side effects include feeling nauseated, dizzy, or tired from the glucose drink. Some people may experience slight bruising from the blood draws.
Recovery from glucose tolerance test
After the test, you can eat, drink, and return to your normal routine. If you felt lightheaded or sick during the test, it should pass quickly.