Requirements prior to the test
- You are to remain on a normal, unrestricted diet for at least 3 days prior to the test.
- You have had no significant illness for 2 weeks prior to test.
- Fasting is required for a period of 10-12 hours prior to the test - no food or fluids such as tea, coffee, or fruit juice. You may have sips of water if you are thirsty.
- Due to the nature of the test, testing is generally done in the morning.
- Certain centres will require you to make an appointment; please telephone your chosen collection centre to check.
- Maintain normal activity prior to the test.
- Avoid smoking for one hour before and during the test.
- Before drinking the glucose, please inform the collection staff if you have any allergies.
What to do during the procedure
- You must remain seated quietly during the test.
- You will be at the collection centre for a minimum of 2 hours.
- You are required to remain in the collection centre until the procedure is completed.
- Bring some reading material or other activity to pass the time.
- If you feel unwell during the test, please inform the collection staff, as you may wish to lie down.
What the procedure involves
- Collection of a fasting blood sample.
- Drinking a 75g bottle of glucose within 5 minutes.
- Collection of a blood sample 1 hour after consuming glucose.
- Collection of a blood sample 2 hours after consuming glucose.
Note: If insulin levels are requested with the GTT, the collection staff will draw blood for this using a separate tube, at the same time as each glucose blood sample is collected.