Skip to content

Understanding Your Medical Test: Purpose, Procedure, and Preparation

Published: August 9, 2026Updated: August 16, 2026

A urine test that measures 5-hydroxyindoleacetate (5-HIAA), a breakdown product of serotonin, to help diagnose carcinoid tumors.

Quick summary

{"Measures serotonin breakdown product in urine","Used to diagnose and monitor carcinoid tumors","Requires a 24-hour urine collection","Certain foods and medications should be avoided before the test","Abnormal results may indicate a neuroendocrine tumor"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
111415-6
Short code
5HIAA
Synonyms
5OH-indoleacetate Msmt Ur
Category
chemistry
Sample
urine
Container
24-hour urine collection container with preservative (HCl or thymol)
Units
N/A
Ref low
2
Ref high
9
Critical range
— – 15 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
High-Performance Liquid Chromatography (HPLC) with electrochemical detection or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
CPT
83497
SNOMED
313295005
Specimen volume
Aliquot of 10-20 mL from complete 24-hour collection
Stability
Refrigerated 2-8°C for up to 5 days; frozen -20°C for longer storage (up to 30 days)
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
48–168 hours
Order
routine

This test is a diagnostic procedure that helps your healthcare provider evaluate your health, identify possible conditions, and guide treatment decisions. Your provider may order it to confirm or rule out a diagnosis, monitor an ongoing condition, or check how well a treatment is working. Understanding why the test is recommended can help you feel more confident and prepared.

The 5-Hydroxyindoleacetate (5-HIAA) urine test measures the amount of 5-HIAA in your urine. 5-HIAA is a waste product created when your body breaks down serotonin, a hormone and neurotransmitter. This test helps doctors check for conditions that affect serotonin production, particularly carcinoid tumors.

The test is performed by a trained member of your care team in a clinic, hospital, or laboratory setting. Depending on the type of test, a small sample such as blood, urine, or tissue may be collected, or imaging equipment may be used to examine a specific area of your body. Most tests take only a short time, and you can usually return to your normal activities soon afterward.

This test requires a 24-hour urine collection. You will be given a special container to collect all urine produced over a 24-hour period. During collection, keep the container refrigerated or in a cool place. Return the container to your healthcare provider as instructed.

Your healthcare provider will give you specific instructions before the test, which may include fasting for a certain number of hours, avoiding certain medications or supplements, or drinking plenty of water. Wear comfortable clothing, bring a list of your current medications, and arrive a little early to complete any paperwork. Be sure to tell your care team if you are pregnant or have any allergies.

Before the test, avoid certain foods that can affect results for 2-3 days, including bananas, avocados, walnuts, pineapples, tomatoes, and eggplants. Also inform your doctor about all medications you are taking, as some medicines (including certain antidepressants, cough medicines, and pain relievers) can interfere with the test results.

Reference range

2.0-9.0 mg/24 hours (or 1.4-6.5 mmol/mol creatinine)N/A

Specimen: urine

Patient should avoid serotonin-rich foods (bananas, avocados, tomatoes, pineapples, plums, walnuts, kiwi) and medications (acetaminophen, aspirin, nicotine, caffeine) for 24-48 hours prior to and during collection as these may falsely elevate results. Collect 24-hour urine specimen with HCl or thymol as preservative.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Why do I need to avoid certain foods before the test?
Some foods contain serotonin or compounds that break down into substances similar to 5-HIAA. Eating these foods can cause false-high results. Your doctor will provide a list of foods to avoid for 2-3 days before and during the collection period.
How long does it take to get results?
Results are typically available within a few days to a week, depending on the laboratory. Your healthcare provider will contact you with the results or discuss them at your follow-up appointment.
What do abnormal results mean?
High 5-HIAA levels may indicate a carcinoid tumor or carcinoid syndrome. However, your doctor will interpret the results in context with your symptoms, medical history, and other tests. Slightly elevated levels may be due to other conditions or dietary factors.
Is the test painful?
No. The test only requires urine collection, which is painless. The 24-hour collection process may be inconvenient but is not uncomfortable.
  1. 1
    MedlinePlus - 5-HIAASource
  2. 2
    May Clinic - Carcinoid tumorsSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy