HIAA - Clinical: 5-Hydroxyindoleacetic Acid (5-HIAA), 24 Hour, Urine

Test Catalog

Test Name

Test ID: HIAA    
5-Hydroxyindoleacetic Acid (5-HIAA), 24 Hour, Urine

Useful For Suggests clinical disorders or settings where the test may be helpful

Biochemical diagnosis and monitoring of intestinal carcinoid syndrome

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

5-Hydroxyindoleacetic acid (5-HIAA) is the major metabolite of serotonin and is excreted in the urine. Intestinal carcinoid tumors along with neuroendocrine tumors can produce excess amounts of 5-HIAA and serotonin especially in individuals with carcinoid syndrome. Carcinoid syndrome is characterized by carcinoid tumors, flushing, heart disease, and hepatomegaly.


Measurement of 5-HIAA in a 24-hour urine specimen can diagnose carcinoid disease with a high specificity.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

< or =8 mg/24 hours

Interpretation Provides information to assist in interpretation of the test results

Elevated excretion of 5-hydroxyindoleacetic acid is a probable indicator of the presence of a serotonin-producing tumor, if pharmacological and dietary artifacts have been ruled out.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Intake of food with a high content of serotonin (avocados, dates, eggplant, all fruit [including bananas, cantaloupe, grapefruit, kiwifruit, melons, pineapple, plantains, plums], all nuts [including hickory nuts, butternuts, pecans, walnuts], and tomatoes and tomato products) within 48 hours of the urine collection could result in falsely elevated 5-hydroxyindoleacetic acid (5-HIAA) excretion.


Numerous drugs affect the excretion of 5-HIAA by different mechanisms, including increased serotonin synthesis, metabolism, and release and inhibition of uptake. The following medications can interfere with 5-HIAA results. If clinically feasible, discontinue the following medications at least 48 hours before specimen collection.

-Acetaminophen (Tylenol or generic versions)



-Cough syrups

-Cold and flu medications


Patient should also avoid caffeinated beverages such as tea and coffee or caffeinated foods for 48 hours before and during specimen collection.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. de Herder W: Biochemistry of neuroendocrine tumours. Best Pract Res Clin Endocrinol Metab 2007 Mar;21(1):33-41

2. Manini P, Andreoli R, Cavazzini S, et al: Liquid chromatography-electrospray tandem mass spectrometry of acidic monoamine metabolites. J Chromatogr B Biomed Sci Appl 2000 July 21;744(2):423-431

3. Mashige F, Matsushima Y, Kanazawa H, et al: Acidic catecholamine metabolites and 5-hydroxyindoleacetic acid in urine: the influence of diet. Ann Clin Biochem 1996;33:43-49

4. Vinik A, Feliberti E, Perry RR: Carcinoid Tumors. In: Endotext. Edited by LJ De Groot, P Beck-Peccoz, G Chrousos. South Dartmouth, MA, MDText.com Inc; 2000. Available at http://www.ncbi.nlm.nih.gov/books/NBK279162/

5. Serotonin syndrome. In POISINDEX System. Edited by RK Klasco, CR Gelman, LT Hill. Greenwood Village, Colorado, Micromedex, 2002

Special Instructions and Forms Library of PDFs including pertinent information and consent forms, specimen collection and preparation information, test algorithms, and other information pertinent to test