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5ohindoleacetateserplmcnc

Published: August 9, 2026Updated: August 10, 2026

This test measures the level of 5-hydroxyindoleacetate (5-HIAA), a breakdown product of serotonin, in your blood to help diagnose and monitor certain neuroendocrine tumors.

Quick summary

{"5-HIAA is a substance produced when your body breaks down serotonin","This test mainly helps diagnose and monitor carcinoid tumors","A 24-hour urine collection is also commonly used alongside this blood test","Certain foods and medications can affect test results","Results help your doctor evaluate treatment effectiveness"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 10, 2026Editorial policy

Key facts at a glance

LOINC
1693-1
Short code
5-HIAA
Synonyms
5OH-indoleacetate SerPl-mCnc
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or plain red top tube
Units
N/A
Ref low
2
Ref high
10
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
High Performance Liquid Chromatography (HPLC) with electrochemical or fluorescence detection, or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
CPT
82157
SNOMED
314180006
Specimen volume
2-5 mL of serum
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
Hemolysis max
50
Lipemia max
100
Icterus max
20
TAT
24–72 hours
Order
routine

What is this test?

The 5-HIAA test measures the amount of 5-hydroxyindoleacetate in your serum or plasma. 5-HIAA is the main breakdown product (metabolite) of serotonin, a hormone and neurotransmitter that helps regulate mood, sleep, and other bodily functions. When your body processes serotonin, it produces 5-HIAA, which can be measured in blood and urine.

Why is it ordered?

This test is primarily ordered to help diagnose and monitor carcinoid tumors, which are rare neuroendocrine tumors that often develop in the digestive tract or lungs. These tumors can produce excess serotonin, leading to elevated 5-HIAA levels. The test may also be used to evaluate symptoms like flushing, diarrhea, and abdominal pain that might suggest a carcinoid tumor.

How is the test performed?

A healthcare professional will draw a blood sample from a vein in your arm. The blood is then sent to a laboratory for analysis. Your doctor may also ask you to collect urine over a 24-hour period, as 5-HIAA is excreted in urine. For the blood test, you may need to fast (not eat) for several hours before the sample is taken.

Preparing for the test

Before the test, inform your doctor about all medications, vitamins, and supplements you are taking. Certain foods (like bananas, avocados, walnuts, and certain cheeses) and medications (including some antidepressants, cough medicines, and pain relievers) can affect serotonin and 5-HIAA levels. Your doctor may ask you to avoid these for 24-48 hours before the test.

Reference range

Reference range: 2.0-10.0 ng/mL (laboratory-specific). Values may vary by methodology and reference population.N/A

Specimen: serum

Patient should fast for 8-12 hours overnight. Avoid serotonin-rich foods for 24-48 hours before collection including bananas, avocados, walnuts, pecans, pineapples, tomatoes, kiwi, plums, and chocolate. Avoid medications that may interfere including MAO inhibitors, tricyclic antidepressants, levodopa, and acetaminophen. Inform physician of all current medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Does the test require fasting?
Yes, you may need to fast for 8-12 hours before the blood test. Your doctor will provide specific instructions.
How long does it take to get results?
Results are typically available within a few days to a week, depending on the laboratory.
Are there any risks with this test?
The risks are minimal and include slight pain, bruising, or bleeding at the injection site. Some people may feel dizzy or faint during or after the blood draw.
Will I need both blood and urine tests?
Your doctor may order both tests for a more complete evaluation. The 24-hour urine test is often used alongside the blood test to get a clearer picture of your 5-HIAA levels over time.
What happens if my results are abnormal?
Abnormal results do not necessarily mean you have a tumor. Your doctor will discuss your results with you and may recommend additional tests, such as imaging scans or biopsies, to determine the cause.
  1. 1
    MedlinePlus - 5-HIAA TestSource
  2. 2
    Mayo Clinic Laboratories - 5-Hydroxyindoleacetic Acid (5-HIAA), SerumSource
  3. 3
    LOINC - 5-Hydroxyindoleacetate [Mass/volume] in Serum or PlasmaSource

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 10, 2026. · Read our editorial policy