This page gives you information about the 5HIAA urine test.

Why am I having a 5HIAA urine test?

Your doctor has asked you to have a 5HIAA urine test to measure certain hormones which your body produces if you have a neuroendocrine tumour (NET).

NET tumours often produce high levels of the hormone serotonin and this hormone will lead to 5HIAA being excreted in the urine.

When there is a chance that you have a bowel or lung NET, one of the methods of diagnosing a tumour is to do the 5HIAA urine test.

By measuring the level of 5HIAA doctors are able to calculate the amount of serotonin in the body.

Why is this urine test important?

Excessive levels of serotonin in the blood can lead to a condition called carcinoid syndrome.

The symptoms of carcinoid syndrome can include:

  • Flushing (redness of the face), which may be more noticeable after drinking alcohol
  • Stomach cramps and diarrhoea
  • Changes in how your heart beats and how the valves in your heart work
  • Bronchospasm (tightening of the muscles that line the airways)

Special precautions

Before you start the test, please avoid the following for 24 hours before the sample is taken and during the 24 hours that you are collecting your sample:

Pecan nuts










Medicines – cough medicines and antihistamines

It is important to avoid these because they all contain serotonin and will provide a false result if you have had them the day before or during the test.

If you are found to have a NET, you will need to repeat this test several times during the course of your treatment but after first test you will only need to provide a single urine sample. We usually repeat the test every 3 to 6 months and before each sample you will need to avoid the items in the list for 24 hours.

How is the test done?

You will need to collect your urine for a 24-hour period, in the container provided. The container will need to be kept in a safe place, away from children.

On the day you are collecting your urine sample you do not need to save the first urine. This can be passed in the toilet but you should make a note of the time on your urine collection container.

For the next 24 hours, each time you pass urine you need to collect it in the container. You could use a jug or bowl to collect the urine in, then pour it into the container you have been given. You need to do this right up until the time you passed your first urine sample (24 hours earlier). For example, if you first passed urine at 7 o’clock in the morning you need to collect all samples until 7 o’clock the following morning.


Once you have completed the 24 hours the container can be taken either to your GP’s surgery or to the hospital to be sent to the laboratory for testing.

Contact information

If you have any questions or would like more information about this test, please contact one of the Macmillan Rare Cancer Nurse Specialists on:

Tel: 07554 330 251

Tel: 07741 331 513

Monday to Thursday, 08.00 am to 4.30 pm


Further information

NET Patient Foundation (Neuroendocrine Cancer)

Freephone: 0800 434 6476


Printable version of this page

The 5HIAA urine test GHPI1543_11_22 Department: Oncology Review due: November 2025 PDF, 155.0 KB, 3 pages
Reference number GHPI1543_11_22
Department Oncology
Review due November 2025