Glucose Tolerance Test (GTT)

On the night before the test

• Please do not eat, chew gum or drink any fluids (except water) for at least 8 hours before the test. It is preferable you do not fast for more than 12 hours.
• Water with no additives can be consumed.
• Record your height and weight.
• Record any recent and current medication.

On the morning of the test

• Bring your medication list and height/weight details.
• Do not physically exert yourself prior to or during the test (including brisk walking to the clinic).
• Avoid smoking for an hour prior to and during the test. If this is not possible, please inform staff.
• Illness can affect glucose tolerance, if you are ill within 3-4 days of the test, contact your doctor to ask whether they want you to postpone the test.
• You will be required to drink a glucose solution within a 5 minute timeframe. This solution contains the following food additives:
  • 330-ascorbic acid
  • 211-sodium benzoate
  • 202-potassium sorbate
  • Sulphites

Do not proceed with the test if you have a known allergy to any of these additives. Contact your doctor and advise your allergy is preventing you from proceeding with the GTT drink.

The test usually takes approximately 2 hours (unless your doctor specifies otherwise).