Oral glucose tolerance test (adults)

You have been referred to the hospital for an oral glucose tolerance test. This leaflet will explain:

• what an oral glucose tolerance test is

• what the risks are

• what will happen before and during the test; and

• when you should receive your results.

We hope this leaflet answers some of the questions you may have. If you have any further questions or concerns, please speak to your doctor or midwife.

What is an oral glucose tolerance test?

To do this test, blood samples are collected before and after you are given a glucose drink. The blood samples are used to measure your blood glucose (sugar) levels.

This test is usually performed to help diagnosis diabetes mellitus (sugar diabetes).

Are there any risks?

The drink you are given is very sweet, and may make you feel sick. If you are sick after having this drink you must tell staff immediately, and they will stop your test.

What should I do before I come for the test?

Please follow these instructions carefully. Failure to do so will make it difficult for your doctor to interpret your results.

• You must fast for at least 8 hours before your test, but not more than 14 hours. This means that from the night before your test, you must not eat anything and must drink only water. Substances in tea, coffee, or cola can affect your results. During this time, do not even drink black coffee and sugar-free (diet) drinks.

• Continue to take your normal medicine on the morning of your test, unless told otherwise by your doctor. If you need to take your morning medicine with food, please discuss this with your doctor.

• Do not chew gum, smoke, vape, or wear a nicotine patch on the morning of your test.

• You may want to bring a book, magazine, or electronic device to read.

What will happen when I have the test?

• A blood sample will be taken from a vein in your arm.

• Your fasting blood sugar level is then checked, using a sample taken by pricking your finger.

  If the sugar level in the finger-prick sample is high, your test will be stopped. You will be advised to return to your GP. If the sugar level in the finger-prick sample is not high the test will continue.

• You will be given a very sweet drink, which contains an exact amount of sugar (glucose). You must drink this within 5 minutes, followed by a drink of water.

  If you are sick after having this drink you must tell staff immediately, and they will stop your test.

• After finishing your drinks, you need to sit quietly for 2 hours close to where the test is carried out. You must not leave to go for a walk or to go shopping. You may drink water during this time but you must not eat, smoke, vape, or chew gum.

• After 2 hours a second blood sample will be taken from a vein in your arm.

• Both blood samples will be sent to the laboratory to measure the amount of glucose in them.

• This is the end of the test. You can now eat and drink normally, and go home.

How long will I be in hospital?

Once the test has started it will take about 2 hours, after which you can go home.

How will I find out my results?

The laboratory will send your results to the doctor or midwife who requested the test. Your doctor or midwife will arrange an appointment to discuss the results with you.

Where can I get more information?

If you have any questions or concerns about this test, please speak to your doctor or midwife who requested the test.