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Glucose Tolerance Test (GTT)

Requirements Prior to the Test

  • You are to remain on a normal, unrestricted diet for at least 3 days prior to test.
  • You have had no acute significant illness for 2 weeks prior to test.
  • Fasting is required for a period of 8-10 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.
  • Maintain normal activity prior to the test.
  • Bring a list of any current medications with you to the collection centre.
  • Avoid smoking for one hour before and during 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 for 30 minutes before and during the test.
  • You will be at the collection centre for a minimum of 2 hours and 45 minutes.
  • 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

  • A fasting blood sample collected.
  • A 75g bottle of glucose to drink within 5 minutes.
  • A 1 hour post glucose blood sample collected.
  • A 2 hour post glucose blood sample collected.


Download Instructions


If insulin levels are requested with the GTT, the collection staff will take blood for this in a separate tube, at the same time each glucose blood sample is collected.

Your Doctor may have ordered an extended GTT test which will require a commitment of 5 hours.