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Collecting urine for 5-hydroxyindoleacetic acid (5-HIAA) measurement - information for patients

Patient information A-Z

This leaflet is intended for patients who have been asked by their doctor or nurse to collect a 24-hour urine sample for 5-HIAA (5-hydroxyindoleacetic acid). If you are unsure whether your doctor has asked you to perform a 24-hour urine collection specifically for 5-HIAA, please contact them for advice.

Please also read our “How to collect a 24 hour urine sample” for general information and collection instructions.

Materials supplied

This leaflet should have been issued with:

  • A five litre container labelled: ‘This urine collection bottle contains: glacial acetic acid’
  • Plastic funnel (on request)
  • Green plastic carrier bag
  • Collection instructions pamphlets

If the collection bottle does not state that it contains glacial acetic acid please contact the clinic or GP practice which gave you the collection bottle as you will need an alternative one. The glacial acetic acid in the bottle acts as a preservative. Please do not discard or rinse out. Please note any warnings or instructions, which are printed on the outside of the urine container.

This preservative is toxic and corrosive. If any bodily contact occurs, immediately wash with plenty of free flowing water. If splashed in eyes, wash with water for at least 10 minutes and seek urgent medical advice.

Always store the container safely out of reach of children.

Background to your test

Patients may have symptoms of diarrhoea or occasional episodes of sweating or flushing because they are producing excess amounts of 5-hydroxytryptamine (also called serotonin). 5HIAA is the breakdown product of 5-hydroxytryptamine and measurement of 5-HIAA assists in determining the appropriate treatment.

You may have been asked to make collections on more than one day. This is because patients may have intermittently raised levels of 5-HIAA. Some foods contain significant amounts of hydroxyindoles which add to the amount of 5HIAA excreted by the body. In addition, some stimulants and over-the-counter supplements increase 5HIAA level in urine.

You are therefore asked to avoid the following for 24hrs before you start the urine collection and during the collection. This is important as otherwise your results may be misleading and lead to further unnecessary tests.

  • Bananas and plantain
  • Plums
  • Pineapples
  • Tomatoes
  • Aubergines
  • Kiwi fruits
  • Avocados
  • Dates
  • Eggplant
  • Hickory nuts (includes pecans)
  • Walnuts
  • Nicotine and smoking
  • Tea
  • Chocolate
  • Coffee
  • Some health food supplements may have 5-hydroxytryptamine (5HT)

If you eat any of the above foods or smoke during the urine collection or in the three days before the collection period, please continue the collection but inform the doctor who asked you to collect the sample.

This information leaflet has been produced by:

Clinical Biochemistry and Immunology; Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust; Box Number 232; Hills Road; Cambridge CB2 0QQ.

We welcome any comments relating to the information you have received and may be contacted on the above address or through duty biochemist by telephone on 0333 103 2220 or email

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