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5-Hydroxyindoleacetic Acid/Creatinine Ratio, Urine

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

This urine test measures 5-HIAA relative to creatinine, helping evaluate serotonin production when a neuroendocrine tumor is suspected.

Quick summary

["An elevated urine 5-HIAA-to-creatinine ratio may indicate increased serotonin production."]

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

Key facts at a glance

LOINC
25109-0
Short code
OH-Lysine/Creat Ur-sRto
Synonyms
OH-Lysine/Creat Ur-sRto
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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

What is this test?

5-hydroxyindoleacetic acid, or 5-HIAA, is a breakdown product of serotonin. This test measures 5-HIAA in urine and compares it with urine creatinine, which helps account for differences in urine concentration.

Why might I need this test?

The test may be used to help evaluate symptoms suggesting excess serotonin production, such as flushing, diarrhea, wheezing, or heart valve changes. It is often considered when a serotonin-producing tumor, including a carcinoid tumor, is being evaluated.

How is the test performed?

A urine sample is collected according to your clinician's instructions. The laboratory measures 5-HIAA and creatinine and reports their relationship; the test may use a single urine sample or a timed collection, such as a 24-hour collection.

How do I prepare for the test?

Follow the exact urine-collection instructions and note the collection time or total volume. Ask your clinician whether you should avoid certain foods, caffeine, alcohol, vigorous exercise, or medications that can affect the result, and do not stop prescribed medicine without guidance.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine 5-HIAA-to-creatinine ratio

Frequently asked questions

What does 5-HIAA measure?
5-HIAA is a breakdown product of serotonin. Its amount in urine can help identify unusually high serotonin production.
Why is creatinine included?
Urine concentration varies with fluid intake and time of day. Comparing 5-HIAA with creatinine helps reduce the effect of these variations.
Does one abnormal result confirm a tumor?
No. An elevated result may support further evaluation, but it does not confirm a tumor by itself and must be interpreted with symptoms, other tests, and possible repeat or confirmatory testing.
  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