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5hiaapnl24hur

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

A 24-hour urine test that measures 5-hydroxyindoleacetic acid (5-HIAA), a breakdown product of serotonin, to help diagnose carcinoid tumors and other conditions.

Quick summary

{"Measures serotonin breakdown product in a 24-hour urine collection","Used to diagnose and monitor carcinoid tumors","Requires avoiding certain foods and medications before the test","Complete 24-hour collection is essential for accurate results","Results help doctors evaluate serotonin-producing tumors"}

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

Key facts at a glance

LOINC
44907-4
Short code
5HIAA24
Synonyms
5HIAA Pnl 24h Ur
Category
chemistry
Sample
serum
Container
24-hour urine collection container with preservative (typically 10 mL of 6N HCl or borate buffer)
Units
N/A
Ref low
2
Ref high
8
Critical range
— – 15 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
High Performance Liquid Chromatography (HPLC) with electrochemical detection or tandem mass spectrometry (LC-MS/MS)
CPT
83497
SNOMED
274441006
Specimen volume
Complete 24-hour collection; aliquot 10-20 mL for analysis
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C): 30 days
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

What is this test?

The 5-Hydroxyindoleacetate (5-HIAA) test measures the amount of 5-HIAA in your urine over a 24-hour period. 5-HIAA is a breakdown product (metabolite) of serotonin, a hormone and neurotransmitter. This test helps doctors check for conditions that affect serotonin production in your body, particularly carcinoid tumors.

How is the test performed?

You will collect all your urine in a special container for exactly 24 hours. Start by urinating into the toilet when you wake up, then collect all subsequent urine in the provided container for the rest of the day and night. The next morning, collect your first morning urine and add it to the container. Keep the container refrigerated during the collection period. Return the completed collection to the laboratory as instructed.

How to prepare for the test

For 48 hours before and during the test, avoid foods rich in serotonin such as bananas, avocados, walnuts, almonds, Brazil nuts, pineapples, tomatoes, eggplants, and certain cheeses. Also avoid medications including cough syrups, antacids, muscle relaxants, and antidepressants (especially SSRIs). Inform your doctor about all medications and supplements you take.

What do the results mean?

Your doctor will interpret your results based on your symptoms and medical history. Elevated 5-HIAA levels may indicate a carcinoid tumor or other neuroendocrine tumor. Normal or low levels do not necessarily rule out all conditions. Your healthcare provider will discuss what your specific results mean for your situation.

Reference range

2.0 - 8.0 mg/24 hours (or 10.5 - 42.0 μmol/24 hours)N/A

Specimen: serum

Patient should avoid serotonin-rich foods for 48-72 hours before and during collection: bananas, pineapples, tomatoes, walnuts, avocados, eggplant, plums. Avoid medications that may interfere: antidepressants (SSRIs, MAOIs), levodopa, acetaminophen, aspirin, reserpine. Collect complete 24-hour urine specimen; record total volume.

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?
Many foods contain serotonin or compounds that can affect serotonin metabolism. Eating these foods during the test period can cause false-positive results, making it appear that you have a tumor when you do not. Following the dietary restrictions ensures accurate results.
What happens if I miss a urine collection during the 24-hour period?
Try to collect every urine sample during the 24-hour period. If you miss a collection, note the time and continue collecting. Inform the laboratory staff when you return the sample so they can note the incomplete collection. In some cases, you may need to restart the collection.
Is the 24-hour urine test painful?
No, the test is not painful. You simply collect urine as you normally would during your daily routine. The only discomfort may be the inconvenience of carrying the container with you and remembering to collect each sample.
How long does it take to get results?
Results are typically available within 3-7 days, depending on the laboratory. Your doctor will contact you with the results or discuss them at your follow-up appointment.
Can I take my regular medications during the test?
You should consult your doctor before the test. Many medications can interfere with test results, including some antidepressants, blood pressure medications, and cough medicines. Your doctor will tell you which medications to avoid and for how long.
  1. 1
    MedlinePlus - 5-HIAASource
  2. 2
    Mayo Clinic Laboratories - 5-HIAA, UrineSource
  3. 3
    National Cancer Institute - 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