Oral Glucose Suppression Test (Investigation Guide)
This test, also called a growth hormone suppression test, checks whether your growth hormone levels suppress normally after drinking a glucose solution, used to confirm or exclude a diagnosis of acromegaly.
Why it's done
- in healthy people, growth hormone levels drop after glucose intake;
- in acromegaly, this normal suppression does not happen;
- confirms excess, unregulated growth hormone production.
What we offer
- an overnight fast beforehand, then a baseline blood sample;
- a glucose drink followed by samples every 30 minutes for 2 hours;
- if growth hormone fails to suppress, a pituitary MRI is arranged to find the cause.
What the test assesses
This test evaluates whether growth hormone suppresses appropriately after a measured glucose drink and is used with IGF-1 results when investigating acromegaly. Blood samples are taken at timed intervals, and interpretation depends on the laboratory method and the wider clinical context.
Preparation and safety
Follow the testing unit’s fasting and medication instructions. Tell the team about diabetes, pregnancy, difficulty tolerating glucose drinks or medicines that affect glucose. Temporary nausea, light-headedness or marked changes in glucose can occur, so the test is performed in a supervised setting.
Results and UK-wide review
Results are interpreted alongside symptoms, IGF-1 and pituitary imaging where appropriate. The findings can usually be reviewed securely by video, while the test itself requires a suitable local investigation unit.