Understanding Your Blood Test: What to Expect and What Your Results Mean
A 24-hour urine test that measures 5-HIA levels to help diagnose and monitor carcinoid tumors.
{"Measures 5-HIA, a breakdown product of serotonin, in a 24-hour urine collection","Used primarily to detect carcinoid tumors (neuroendocrine tumors)","Requires complete 24-hour urine collection for accurate results","Elevated levels may indicate carcinoid syndrome or tumor","Results help doctors monitor treatment effectiveness"}
Key facts at a glance
- LOINC
- 25971-3
- Short code
- 5-HIAA 24h U
- Synonyms
- 5OH-indoleacetate 24h Ur-sCnc
- Category
- chemistry
- Sample
- urine
- Container
- 24-hour urine collection container with preservatives (typically 10 mL of 6M HCl as preservative)
- Units
- N/A
- Ref low
- 2
- Ref high
- 9
- Critical range
- — – 50 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- High Performance Liquid Chromatography (HPLC) with electrochemical detection or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
- CPT
- 83497
- SNOMED
- 274517006
- Specimen volume
- Complete 24-hour collection, typically 1000-2000 mL total volume
- Stability
- Refrigerated: 7 days; Frozen at -20°C: 30 days; Protect from light
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 72–168 hours
- Order
- routine
What is this test and what does it check?
The 5-Hydroxyindoleacetate (5-HIA) test measures the amount of 5-HIA in your urine over a 24-hour period. 5-HIA is a byproduct of serotonin, a hormone and neurotransmitter produced by certain cells in your body. When you collect your urine for 24 hours, the test can detect abnormal levels of 5-HIA that may indicate the presence of a carcinoid tumor.
Why might my healthcare provider order this test for me?
This test is primarily ordered to help diagnose carcinoid tumors, which are rare neuroendocrine tumors that often develop in the digestive tract or lungs. Carcinoid tumors can produce excess serotonin, leading to elevated 5-HIA levels in urine. The test may also be used to monitor how well treatment is working if you have been diagnosed with a carcinoid tumor.
How should I prepare for the test before my appointment?
Your doctor may ask you to avoid certain foods and medications before the test, as these can affect results. Foods to avoid include bananas, pineapples, tomatoes, walnuts, and avocados. You should also inform your doctor about any medications you're taking, especially antidepressants, cough medicines, or blood pressure medications. Your healthcare provider will give you specific instructions on how to collect the urine sample.
How is the test performed during my visit?
You will receive a special container for collecting all urine over a 24-hour period. On the first day, urinate into the container when you wake up in the morning and discard that first sample. Then, collect all urine for the next 24 hours, including the first morning urine on the second day. Keep the container refrigerated during the collection period. Return the container to your lab as instructed.
Understanding your results: what the numbers mean and when to talk with your doctor
Normal 5-HIA levels vary by laboratory, but typically range from 2 to 8 milligrams per 24 hours. Elevated levels may suggest carcinoid tumor or carcinoid syndrome. Your doctor will interpret your results based on your symptoms, medical history, and other test findings. A single elevated result does not confirm cancer—follow-up testing is usually needed.
Reference range
2.0-9.0 μmol/24 hr (0.4-1.8 mg/24 hr)N/A
Patient should avoid foods rich in serotonin for 48 hours before and during collection, including bananas, avocados, plums, walnuts, pineapples, tomatoes, and certain cheeses. Avoid medications that may interfere including antidepressants (SSRIs, MAOIs), acetaminophen, aspirin, and caffeine. Collect all urine for exactly 24 hours; discard first morning void and include final morning void at end of collection. Keep container refrigerated during collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The 5-HIA test is primarily used to diagnose and monitor carcinoid tumors, which are slow-growing neuroendocrine tumors that can occur in the gastrointestinal tract, lungs, or other organs. These tumors may produce hormones causing symptoms like flushing, diarrhea, and abdominal pain (carcinoid syndrome). The test helps detect excess serotonin production, assess tumor activity, and evaluate treatment response. It may also be used to rule out carcinoid tumors when patients have unexplained abdominal symptoms or to screen individuals with genetic conditions that increase carcinoid risk.
Frequently asked questions
Is the 24-hour collection inconvenient?
Does the test hurt?
How long does it take to get results?
What if I forget to collect urine for one time period?
Can I still take my regular medications?
Sources
- 1
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
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