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5-Hydroxyindoleacetic Acid (5-HIAA)

Published: July 27, 2026Updated: August 25, 2026

5-HIAA is a metabolite of serotonin, primarily measured to diagnose and monitor neuroendocrine tumors such as carcinoid tumors.

Quick summary

5-HIAA is a serotonin metabolite used to diagnose neuroendocrine tumors.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
mg/day
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche 5-HIAA, Diasora 5-HIAA
interpretation: {"text":"0–6 mg/day: Indicates no significant elevation of serotonin metabolism, reducing suspicion of neuroendocrine tumors.","label":"Normal"}; {"text":">6 mg/day: Suggests increased serotonin metabolism, potentially indicating the presence of neuroendocrine tumors such as carcinoid tumors.","label":"Elevated"}

5-Hydroxyindoleacetic acid (5-HIAA) is a major metabolite of serotonin, a neurotransmitter and hormone involved in various physiological processes, including mood regulation and digestion.

The measurement of 5-HIAA in urine or blood is crucial for diagnosing and monitoring neuroendocrine tumors, particularly carcinoid tumors, which can secrete excessive serotonin.

Elevated levels of 5-HIAA can indicate the presence of these tumors, while normal levels help rule out such conditions, making it a valuable diagnostic tool.

Frequently asked questions

What is the normal range for 5-HIAA?
The normal range for 5-HIAA is typically 0–6 mg/day.
What conditions can cause elevated 5-HIAA levels?
Elevated 5-HIAA levels can be caused by neuroendocrine tumors, particularly carcinoid tumors, as well as certain medications and dietary factors.
  1. 1
    Mayo Clinic: 5-HIAA TestSource
  2. 2
    American Cancer Society: 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

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Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy