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Oral Glucose Tolerance Test - Acromegaly

Patient information A-Z

You will receive a separate appointment letter for this test.

What is an oral glucose tolerance test?

Your doctor has referred you for an Oral Glucose Tolerance Test (OGTT) to assess your growth hormone levels.

Glucose should suppress growth hormone levels. This test is used to diagnose whether you produce too much growth hormone, which is a rare disorder, known as acromegaly. Acromegaly may cause some of the following symptoms: enlargement of the hands, feet and tongue, coarse facial features, sweating, headaches, joint pain, tiredness, snoring and visual impairment. This test is also used to monitor patients who have previously been treated for acromegaly to ensure their disease is in remission.

Do I need to prepare for the test?

You will need to fast from midnight the night before your test. Only plain water can be drunk during the fasting period and the test. If you have diabetes please let us know before you attend for the test.

What happens during the test?

You will need to arrive at the endocrine investigation unit by 09:00.

A fine plastic tube called a cannula will be inserted into a vein in your arm, to allow us to take blood samples at regular intervals. After a short resting period and the first blood test, you will be given a glucose drink. Blood samples will be taken to measure glucose and growth hormone at 30 minute intervals. During the test you are not allowed anything to eat and only plain water to drink.

How long will the test take?

You will be in the endocrine investigation unit for at least two and a half hours. You may like to bring a book or magazine to read as well as something to eat at the end of the test.

Will I experience any side effects?

Occasionally some people experience nausea and headaches during the test, these usually resolve within a short time.

When will I get my results?

Results will be discussed at your next clinic appointment.

Any other questions?

Please contact the endocrine unit on 01223 217848.

The timing of the test is important, so please attend at the time specified on your appointment letter. If you are unable to attend your appointment, please contact the endocrine unit to rearrange it.

General Information

Discounted parking is available for patients attending clinic appointments over three hours duration. Please present your appointment letter to receive this.

Food and drink - there is a coffee shop in the treatment centre atrium and further food and drink facilities in the main hospital concourse.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151