5-HIAA

Also Known As

HIAA

Serotonin Metabolite

Formal Name

5-hydroxyindoleacetic Acid

This article was last reviewed on

April 15, 2019.

This article waslast modified on October 7, 2019.

At a Glance

Why Get Tested?

To help diagnose and monitor treatment for a carcinoid tumor that produces serotonin

When To Get Tested?

When you have symptoms suggestive of a carcinoid tumor, such as flushing, abdominal pain, diarrhea, and/or wheezing; at intervals following treatment

Sample Required?

A 24-hour urine sample; rarely, a random urine sample or a blood sample drawn from a vein

Test Preparation Needed?

You may be instructed to avoid certain foods and medications prior to this test. (For more details, see the "What is being tested?" section below.)

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

5-hydroxyindoleacetic acid (5-HIAA) is the primary breakdown product (metabolite) of serotonin, a chemical substance (neurotransmitter) that transmits messages between nerve cells. This test measures the amount of 5-HIAA in the urine or blood.

Serotonin is produced as needed by the nervous system, mainly the brain, but also special cells in the bronchial tubes (lungs) and gastrointestinal (GI) tract. It helps transmit nerve impulses and constrict blood vessels, participates in the wake-sleep cycle, and affects mood. After it is used by the body, serotonin is broken down in the liver, and its metabolites, including 5-HIAA, are eliminated in the urine.

Ordinarily, only small varying amounts of 5-HIAA are present in the urine. Large quantities of serotonin and 5-HIAA may be produced, however, by some carcinoid tumors. Carcinoid tumors are slow-growing noncancerous or cancerous neuroendocrine masses that can form in the GI tract, especially in the appendix, and in the lungs. About 2 out of every 3 carcinoid tumors are found in the GI tract with most of the rest occurring in the lungs, although they may affect other organs as well.

According to the American Cancer Society, there are about 8,000 neuroendocrine tumors or cancers that start in the GI tract and 2,000 to 4,000 that start in the lungs diagnosed each year in the United States. Many more of these tumors may exist, but most remain small and do not cause any symptoms. When carcinoid tumors are discovered in asymptomatic patients during surgical procedures performed for other reasons, they are called "incidental" tumors. A small percentage of these tumors may eventually grow large enough to cause obstructions in the intestines or bronchial tubes of the lungs.

About 10% of carcinoid tumors, primarily those found in the GI tract affecting the liver, will produce enough serotonin to cause symptoms, such as flushing of the face, diarrhea, a rapid heart rate, and wheezing, which are referred to as carcinoid syndrome. The serotonin that causes carcinoid syndrome may be released continuously or intermittently and can lead to significantly increased quantities of 5-HIAA in the blood and urine.

How is the sample collected for testing?

A 24-hour urine sample is preferred for the 5-HIAA test because the level of the metabolite can vary during the day. For a 24-hour urine collection, all of the urine produced should be saved for a 24-hour period. It is best to keep the sample in a cool, dark place, such as a refrigerator.
A random urine sample is sometimes tested, usually along with a urine creatinine level, when a 24-hour sample is not feasible. The random sample is not as accurate, however, and if excess 5-HIAA is released intermittently, then it may be missed.
Sometimes a blood sample is drawn from a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

Test preparation is important for accurate 5-HIAA test results. Foods rich in serotonin such as avocados, bananas, pineapples, plums, cantaloupes, grapefruits, plantains, melons, kiwi fruits, walnuts, hickory nuts, butternuts, pecans, tomatoes, and eggplants can interfere with 5-HIAA measurement and should be avoided for 3 days prior to and during sample collection. There are also a variety of drugs that can affect metabolism of serotonin and thus the 5-HIAA test. It is important that you talk to your healthcare provider before decreasing or discontinuing any medications.

Some laboratories request for overnight fasting prior to collection of blood samples.

Common Questions

How is the test used?

The 5-hydroxyindoleacetic acid (5-HIAA) test is used to help diagnose and monitor carcinoid tumors. It may be ordered by itself or along with a blood serotonin and/or chromogranin A level.
When is it ordered?
This test is primarily ordered when you have signs and symptoms suggestive of a carcinoid tumor.

Some examples include:

Flushing of the face and neck (appearance of deep red color, usually with sudden onset)

Diarrhea, abdominal pain, nausea, vomiting

Rapid heart rate

Wheezing, coughing, difficulty breathing

This test may also be ordered at intervals when monitoring the effectiveness of treatment for a carcinoid tumor.
What does the test result mean?

A significantly increased level of 5-HIAA when you have carcinoid syndrome symptoms is suggestive but not diagnostic of a carcinoid tumor. In order to diagnose the condition, the tumor itself must be located, biopsied, and examined by a pathologist. Your healthcare practitioner will frequently follow an abnormal test result with an order for an imaging scan to help locate any tumor(s) that may be present.

You may still have a carcinoid tumor even if your 5-HIAA level is normal. Some carcinoid tumors do not produce serotonin or only produce it intermittently.

If you have no symptoms and normal levels of 5-HIAA, it is unlikely you have a carcinoid tumor that produces serotonin.

If you are being monitored following treatment for carcinoid tumor, decreasing levels of 5-HIAA indicate a response to treatment, while increased or rising levels indicate that treatment has not been successful.
Is there anything else I should know?
There are a variety of drugs that can affect the 5-HIAA test:

Medications that can increase 5-HIAA include acetaminophen, caffeine, ephedrine, diazepam (Valium®), fluorouracil, glyceryl guaiacolate (an ingredient found in some cough medicines), melphalan (Alkeran®), mephenesin, methamphetamine (Desoxyn), methocarbamol (Robaxin®), naproxen, nicotine, phenacetin, phenmetrazine, phenobarbital, phentolamine, rauwolfia, and reserpine.

Medications that can decrease 5-HIAA include aspirin, chlorpromazine (Thorazine), corticotropin, dihydroxyphenylacetic acid, ethyl alcohol, gentisic acid, homogentisic acid, hydrazine derivatives, imipramine(Tofranil®), isocarboxazid (Marplan), levodopa, MAO inhibitors, heparin, isoniazid, methenamine, methyldopa(Aldomet®), perchlorperazine, phenothiazines (Compazine®), promazine, promethazine (Mepergan®) and tricyclic antidepressants.

You should talk to your healthcare provider before decreasing or discontinuing any medications.
Why do I have to collect my urine for 24 hours?

The level of 5-HIAA in the urine varies throughout the day. By collecting all urine for 24 hours, the amount of 5-HIAA in the urine can be averaged over the entire day and increases of 5-HIAA will be detected more easily than in a single random urine sample.
Will my results be accurate if I must continue to take my medication?

If the drug is one that can increase or decrease the amount of serotonin and 5-HIAA, then your results may be affected. However, it is up to your healthcare provider and you to decide whether or not your medication can be safely stopped prior to and during the test collection. If your drugs must be taken, then your healthcare practitioner will interpret the test results with this in mind.
Are some people at a higher risk for developing a carcinoid tumor?

Anyone at any age can develop a carcinoid tumor but, according to the American Cancer Society, the average age at diagnosis is usually in the early 60s. People with a family history of multiple endocrine neoplasia (MEN1), a genetic condition that increases a person's risk of developing tumors in the endocrine system glands, may be at higher risk for developing a carcinoid tumor.

See More Common Questions See Less Common Questions

View Sources

Sources Used in Current Review

2019 review performed by Hui Li, PhD, DABCC, FACB, FCACB, Clinical Chemist, Laboratory/Medical Director, Dynacare.

Ito T. et. al. Carcinoid-syndrome: recent advances, current status and controversies. Curr Opin Endocrinol Diabetes Obes. 2018 Feb;25(1):22-35. Accessed online through https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5747542/pdf/nihms919791.pdf.

Kaltsas G. et. al. ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors: Pre- and Perioperative Therapy in Patients with Neuroendocrine Tumors. Neuroendocrinology. 2017 Sep; 105(3): 245–254. Accessed online through https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5637287/?report=reader#. Accessed 4/5/2019.

Adaway, J. et. al. Serum and plasma 5-hydroxyindoleacetic acid as an alternative to 24-h urine 5-hydroxyindoleacetic acid measurement. Ann Clin Biochem. 2016;53:554–560. Accessed online through https://journals.sagepub.com/doi/full/10.1177/0004563215613109?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed. Accessed 4/5/2019.

(© 1995–2019) 5-Hydroxyindoleacetic Acid (5-HIAA), 24 Hour, Urine. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at https://www.mayocliniclabs.com/test-catalog/2011/Clinical+and+Interpretive/9248. Accessed on 4/5/2019.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO. Pp 497-498.

(2005). Gastrointestinal Carcinoid Tumors, A Detailed Guide. American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/CRI/CRI_2_3x.asp?dt=14.

Nanda, R. (2005 April 15, Updated). 5-HIAA. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003612.htm.

Brose, M. (2004 August 3, Updated). Carcinoid Syndrome. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000347.htm.

Zuetenhorst, J. et. al. (2004 July 9). Daily Cyclic Changes in the Urinary Excretion of 5-Hydroxyindoleacetic Acid in Patients with Carcinoid Tumors. Clinical Chemistry [On-line journal]. Available online at http://www.clinchem.org/cgi/content/full/50/9/1634.

Datta, V. (2005 May 17, Updated). Serum serotonin level. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003562.htm.

Sweeney, J. and Rosemurgy, A. (1997 January/February). Carcinoid Tumors of the Gut. Cancer Control Journal v4 (1) [On-line journal]. Available online at https://www.moffitt.usf.edu/pubs/ccj/v4n1/article2.htm.

Strosberg, J. et. al. (2006 January). Selective Hepatic Artery Embolization for Treatment of Patients With Metastatic Carcinoid and Pancreatic Endocrine Tumors. Cancer Control Journal v13 (1) [On-line journal]. Available online at https://www.moffitt.usf.edu/pubs/ccj/.

Johnson, R. et. al. (2003 November). Ethanol Origin in Postmortem Urine: A LC/MS Determination of Serotonin Metabolites. Federal Aviation Administration [On-line Medicine Technical Report]. Available online through http://www.faa.gov.

Dugdale, D. (2008 November 10). 5-HIAA. MedLinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003612.htm. Accessed July 2010.

(Revised 2009 June 06). Detailed Guide: Gastrointestinal Carcinoid Tumors. American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/CRI/CRI_2_3x.asp?rnav=cridg&dt=14. Accessed July 2010.

(Revised 2010 March 18). Detailed Guide: Lung Carcinoid Tumor. American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/CRI/CRI_2_3x.asp?rnav=cridg&dt=56. Accessed July 2010.

(2010 February). Carcinoid Tumor. Cancer.Net, American Society of Clinical Oncology [On-line information]. Available online at http://www.cancer.net/patient/Cancer+Types/Carcinoid+Tumor. Accessed July 2010.

(Modified 2008 May 16) Gastrointestinal Carcinoid Tumors Treatment (PDQ®), Health Professional Version [On-line information]. Available online at http://www.cancer.gov/cancertopics/pdq/treatment/gastrointestinalcarcinoid/HealthProfessional. Accessed July 2010.

Santacroce, L. and Diomede, L. (Updated 2009 November 19). Malignant Carcinoid Syndrome. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/282515-overview. Accessed July 2010.

Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds (2005). Harrison's Principles of Internal Medicine, 16th Edition, McGraw Hill, Pp 2224-2225.

Garg, S. (Updated 2014 February 6). 5-Hydroxyindoleacetic Acid (5-HIAA). Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2089202-overview. Accessed February 2014.

Tebbi, C. (Updated 2014 January 27). Carcinoid Tumor. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/986050-overview. Accessed February 2014.

(© 1995–2014). 5-Hydroxyindoleacetic Acid (5-HIAA), Urine. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/9248. Accessed February 2014.

Frank, E. et. al. (Updated 2013 September). Carcinoid Tumors. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/CarcinoidTumors.html?client_ID=LTD. Accessed February 2014.

Dugdale, D. (Updated 2012 September 9) 5-HIAA. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003612.htm. Accessed February 2014.

(Updated 2012 July 10). Carcinoid Syndrome. Mayo Clinic [On-line information]. Available online at http://www.mayoclinic.org/diseases-conditions/carcinoid-syndrome/basics/definition/CON-20027127. Accessed February 2014.

Ask a Laboratory Scientist

This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.

Please indicate whether you are a

Country

I have read and agree to the Privacy Policy (read the Privacy Policy)

I have read and agree to the Terms of Use (read the Terms of Use)

I agree to the disclaimer (read the disclaimer).

Disclaimer

Thank you for using the Consumer Information Response Service ("the Service") to inquire about the meaning of your lab test results. The Service is provided free of charge by the American Society for Clinical Laboratory Science, which is one of many laboratory organizations that supports Lab Tests Online.
Please note that information provided through this free Service is not intended to be medical advice and should not be relied on as such. Although the laboratory provides the largest single source of objective, scientific data on patient status, it is only one part of a complex biological picture of health or disease. As professional clinical laboratory scientists, our goal is to assist you in understanding the purpose of laboratory tests and the general meaning of your laboratory results. It is important that you communicate with your physician so that together you can integrate the pertinent information, such as age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), to determine your health status. The information provided through this Service is not intended to substitute for such consultations with your physician nor specific medical advice to your health condition.
By submitting your question to this Service, you agree to waive, release, and hold harmless the American Society for Clinical Laboratory Science and its affiliates or their past or present officers, directors, employees, agents, and Service volunteers (collectively referred to as "ASCLS") and the American Association for Clinical Chemistry and its affiliates or their past or present officers, directors, employees, agents, and Service volunteers (collectively referred to as "AACC") from any legal claims, rights, or causes of action you may have in connection with the responses provided to the questions that you submit to the Service.
AACC, ASCLS and its Service volunteers disclaim any liability arising out of your use of this Service or for any adverse outcome from your use of the information provided by this Service for any reason, including but not limited to any misunderstanding or misinterpretation of the information provided through this Service.

See More See Less

On This Site

Elsewhere On The Web

Ask a Laboratory Scientist