5-HIAA
5-HIAA is a metabolite of the 5-hydroxytryptamine (5-HT) neurotransmitter (also known as serotonin). Increased 5HT turnover is characteristic of carcinoid syndrome.
Tumours may occur anywhere in the GI tract and can typically secrete 5-HT, catecholamines, prostaglandins and histamine. Carcinoid syndrome can be characterised by symptoms of flushing and diarrhoea. Abdominal pain, bronchial asthma, heart failure and pellagra may also be present. However, it is usually only associated with the mid gut tumours that have metastasized to the liver and are found predominantly in the ileum and appendix.
Carcinoid syndrome, characterised by symptoms of flushing and diarrhoea. Abdominal pain, bronchial asthma, heart failure and pellagra may also be present.
Reference intervals will be given with the report.
Certain foodstuffs may cause false positive results. These include: aubergines, avocados, bananas, caffeine, pineapples, plums, tomatoes, walnuts, and medications such as cough mixtures containing guaifenesin/glycerol guaiacolate.
The patient must follow the specified diet for 72hrs with the urine being collected in the last 24hrs (patient diet sheet for 5HIAA collection is provided together with the acidified container).
Requesting clinicians should ensure relevant medications from the diet sheet are removed or submitted as clinical details at receipt.
Samples with pH>6.0 are unsuitable for this assay.
Not currently performed in house; this is a referred test. Referral laboratory is Synnovis.
Record last updated
September 8, 2025
Sample Container
24hr Urine Bottle (with acid warning label)
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Test Results
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Yes. Please email your request to Imperial.nwlpcustomerservice@nhs.net
Results are communicated to clinical staff and are normally not communicated direct to patients either on telephone requests or in written report. If you need to contact us please click here to view the contact details page
Please contact the Customer Service Team Monday to Friday from 8:30am – 6:00pm on 0203 313 5353. Alternatively, see the Pathology User Guide for how to contact the relevant department. If advice is not urgent you can also email your query to Imperial.nwlpcustomerservice@nhs.net
Additional tests may be added by discussion with the relevant laboratory. The time limit for adding additional tests to a sample already received in the laboratory will depend on the type of sample and the department it was sent to.
Information on the repertoire of tests performed by pathology, including reference ranges, turnaround times and specimen requirements, can be found in the test directory.
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NWLP operates UKAS accredited medical laboratories as per the references below. The current scope of accreditation for all NWLP’s laboratories can be found on the UKAS website.
See the following UKAS ref numbers:
- Clinical Biochemistry Ref: 8673
- Haematology and Blood Transfusion Ref: 8674
- Infection & Immunity Sciences (Including Immunology, Virology, Microbiology and Histocompatibility and Immunogenetics ) Ref: 8659
- Cellular Pathology (Including Histopathology, Cytology and Molecular Pathology) Ref: 9615
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UKAS requires the laboratories to be accredited for a particular repertoire/scope (ISO15189), any changes or additions to repertoire require assessment by UKAS (extension to scope).
The BD Hospital Tube Guide, BD GP Tube Guide and BD Paediatric Tube Guide provide visual references to the correct tube types and collection instructions.
Home testing
INSTRUCTION SHEET FOR BLOOD SAMPLE COLLECTION
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Our accreditations
Upholding excellence in diagnostic standards
Our laboratories are accredited by the UK Accreditation Service (UKAS) against the international standard ISO15189:2022. UKAS is the accreditation body for the UK that assesses medical laboratories.
Find out more about our accreditations on the UKAS website.
UKAS website