Urine tests for neuroendocrine tumours (NETs)

Neuroendocrine tumours sometimes release high amounts of serotonin. This breaks down into a substance called 5-HIAA. Your doctor can test for this in your urine.

Why you might have a urine test

A raised amount of 5-HIAA in your urine can be a sign of a neuroendocrine tumour. It can also be caused by other medical conditions. Not everyone with a high level of 5-HIAA in their urine has a neuroendocrine tumour.

What happens

For the test, you may be asked to collect all your urine over 24 hours to measure the amount of 5-HIAA in it. Or you might be able to give one urine sample.

Your nurse or doctor will give you a container to collect your urine in.

Preparing for your test

For a few days before and during your test, you should avoid eating foods that are rich in serotonin. These include:

  • bananas
  • tomatoes
  • avocado
  • aubergine
  • walnuts
  • pineapple
  • kiwi fruit
  • plums
  • alcohol
  • tea
  • coffee

Some medicines can also affect the level of 5-HIAA in your urine. You might need to stop taking them for a few days before your test. Let your doctor or nurse know about any medicines or herbal remedies you are taking.

Collecting your urine

You take a large container home to collect your urine. The container contains a small amount of acid. Do not throw this away. Be sure not to get it on your skin as it could burn. If any acid splashes in your eyes or onto your skin, wash with plenty of water and phone your doctor for advice.

When you’re ready to start the test, go to the toilet to empty your bladder. Make a note of the time and date on the container. You then need to collect all the urine you pass in the next 24 hours.

It’s easier to collect your urine in a smaller jug or bowl and then pour it into the container.

Ideally keep the container at a cool temperature. After the 24 hours, you return the container to the hospital.

Getting your results

You usually get your results within 2 to 4 weeks at a follow up appointment. 

Waiting for test results can be a worrying time. You can contact your specialist nurse if you’re finding it hard to cope. It can also help to talk to a close friend or relative about how you feel.

For support and information, you can call the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday.

Other tests

Most people have several tests to diagnose a NET. You can find out what other tests you might have in your specific NET section.

  • The Royal Marsden Manual of Clinical Nursing Procedures, 9th edition
    L Dougherty and S Lister (Editors)
    Wiley-Blackwell, 2015

  • Gastroenteropancreatic neuroendocrine neoplasms: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
    M. Pavel and others
    Annals of Oncology 2020, Vol 31, Issue 5 

  • Pulmonary neuroendocrine (carcinoid) tumors: European Neuroendocrine Tumor Society expert consensus and recommendations for best practice for typical and atypical pulmonary carcinoids
    ME Caplin and others
    Annals of Oncology, 2015
    Volume 26, Issue 8

  • Cancer: Principles and Practice of Oncology (11th edition)
    VT DeVita and others
    Wolters Kluwer, 2019

Last reviewed: 
11 Mar 2021
Next review due: 
11 Mar 2024

Related links