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5-Hydroxyindoleacetic acid (5-HIAA) in urine

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

This test measures the amount of 5-hydroxyindoleacetic acid, a breakdown product of serotonin, in your urine over a 24-hour period. It helps assess serotonin-related conditions, such as carcinoid syndrome.

Quick summary

["This test helps diagnose or monitor serotonin-related disorders by checking serotonin metabolism in your urine."]

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

Key facts at a glance

LOINC
72466-6
Short code
JWH-250 5OH-pentyl Ur Ql Cfm
Synonyms
JWH-250 5OH-pentyl Ur Ql Cfm
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
confirm
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order a 24-hour urine 5-HIAA test if you have symptoms like flushing, diarrhea, or wheezing that could suggest a serotonin-producing tumor, such as carcinoid tumor. It may also be used to check if treatment is working or to monitor for recurrence.

What to Expect Before the Test

You’ll collect all urine for 24 hours in a special container. Start and end timing at the same time each day. Drink plenty of fluids to ensure full collection. Avoid certain medications (like SSRIs) that could affect results.

During the Test

No special preparation is needed beyond the 24-hour urine collection. The lab processes the sample to measure 5-HIAA levels.

Possible Results and Interpretation

Higher-than-normal levels may indicate serotonin-producing tumors or other serotonin-related disorders. Lower-than-normal levels may suggest a deficiency or medication effects. Your doctor will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Urine 5-HIAA

Frequently asked questions

What does a high 5-HIAA level mean?
A significantly elevated 5-HIAA level in urine is strongly suggestive of carcinoid syndrome or other serotonin-secreting tumors. This condition can cause symptoms like abdominal pain, diarrhea, flushing, and heart valve damage. Early diagnosis helps guide treatment decisions.
Could low 5-HIAA levels indicate anything?
Low 5-HIAA levels alone may not indicate a specific disorder but could be seen in people with serotonin deficiency or those taking medications that lower serotonin metabolism. Always discuss results with your doctor.
How often should this test be repeated?
Your doctor will determine follow-up testing based on initial results and your clinical needs. If you have a known serotonin-related condition, repeat tests may be scheduled to monitor progression or treatment response.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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