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5-Hydroxindoleacetic Acid (Urine)

Does this test have other names?

5-Hydroxindoleacetic acid urine, 5-HIAA, HIAA

What is this test?

This test measures the amount of 5-hydroindoleacetic acid (5-HIAA) in your urine.

Your liver breaks down the hormone serotonin into 5-HIAA, a waste product normally sent from your body in your urine. Tumors called functioning carcinoids secrete serotonin. Carcinoid tumors are found in the intestinal tract, lungs, appendix, and other body tissues.

Why do I need this test?

You may need this test if you have symptoms of a carcinoid tumor. Carcinoid tumors can occur anywhere, but most start in the appendix or small bowel. Signs and symptoms include:

  • Flushing in your face and neck

  • Diarrhea and abdominal cramps

  • Nausea and vomiting

  • Low blood pressure

  • Unexplained weight loss

  • Irregular heartbeat

  • Watery eyes

  • Asthma-like respiratory symptoms

  • Sexual dysfunction in men

What other tests might I have along with this test?

Your doctor may also order a biopsy to help diagnose a tumor. Your doctor may also order a liver scan if he or she suspects that the tumors have spread.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Normal results are 3 to 15 milligrams (mg) of 5-HIAA over 24 hours. Women generally have lower levels than men.

Higher levels of 5-HIAA may mean you have:

  • Carcinoid tumors

  • Noncarcinoid tumors

  • Cystic fibrosis

  • Malabsorption

Lower levels of 5-HIAA may mean you have:

  • Depression

  • Migraines

How is this test done?

This test requires a 24-hour urine sample. For this sample, you must collect all of your urine for 24 hours. Empty your bladder completely first in the morning without collecting it and note the time. Then collect your urine every time you go to the bathroom over the next 24 hours.

Does this test pose any risks?

This test poses no known risks.

What might affect my test results?

Eating certain foods containing serotonin can raise 5-HIAA levels. These foods include:

  • Cheese

  • Bananas

  • Pineapple

  • Kiwi

  • Plums

  • Tomatoes

  • Eggplant

  • Avocados

  • Certain nuts, including walnuts and pecans

Certain drugs can raise or lower your 5-HIAA levels. These include:

  • Aspirin

  • Acetaminophen

  • Ethyl alcohol

  • Some antidepressants

Strenuous exercise can also raise your 5-HIAA levels.

How do I get ready for this test?

Don't eat foods containing serotonin for at least three days before the test or during the testing period. You may also need to stop taking certain medications before the test. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.