Glucose tolerance test

Information about the glucose tolerance test.

This pamphlet provides information on the glucose tolerance test (screening for diabetes/gestational diabetes).


The test will be carried out at the outpatient blood test department. Your department will provide you with the time and date of the test. Remember to bring your health card.

Why do I need the test?  

A glucose tolerance test is mainly carried out to determine whether a person has diabetes or gestational diabetes.

Preparing for the test

  • Avoid physical exercise on the day of the test.
  • Take any medication as usual.
  • You are not permitted to drink alcohol 24 hours before the test.
  • Do not eat for 12 hours before the test.
  • You may only drink water, tea and coffee (without sugar and milk) until two hours before the test.
  • You may drink water until one hour before the test.
  • You may not smoke tobacco or use nicotine products two hours before the test.
  • Rest in an upright position for at least 15 minutes before the test.

If you have any questions, please contact the doctor or department that has ordered the test.

About the test

  • The test begins with 15 minutes of rest.
  • If you are not pregnant, a blood sample will be taken from your arm (pregnant women will have a blood sample taken after the test).
  • Afterwards, you will be asked to drink a mixture of water and glucose (dextrose), possibly flavoured with lemon. The mixture tastes sweet but is not unpleasant. It is important that you drink the entire mixture within approximately five minutes.
  • A second blood sample will be taken two hours later to measure any changes in your blood sugar levels.
  • You should rest during the test. Perhaps bring some reading material, to help occupy yourself during the wait.

How long does the test take?

The test takes about 2½ hours.

Test results

You will receive the test results no later than at your next appointment.


Contact your department to schedule a new appointment.


The Illustration shows outpatient blood test department in Center 1 on a map
The outpatient blood test department in Center 1 in orange at Hvidovre Hospital.