Oral glucose tolerance test
Also written: OGTT
What it measures
Blood sugar before and after drinking a standard glucose load, measured at set time points.
Why it is ordered
Used when a fasting sugar is inconclusive, and in pregnancy screening.
How to prepare
🔴 Fast exactly as instructed, eat normally for several days beforehand (strict dieting distorts the result), and stay at the facility for the whole test.
Units
mg/dL ↔ mmol/L — convert here
What to ask
- How long must I stay
- How many blood draws
- May I drink water during the test
This page does not include reference ranges and does not say whether your number is high or low. Reference ranges differ between laboratories and between people — read yours on your own report, with your clinician.