A 24-hour urine sample is needed. You'll need to collect your urine over 24 hours in a container provided by the lab. Your health care provider will tell you how to do this. Follow instructions exactly.

Your provider will instruct you, if necessary, to stop taking medicines that may interfere with the test.

Medicines that can increase 5-HIAA measurements include acetaminophen (Tylenol), acetanilide, phenacetin, glyceryl guaiacolate (found in many cough syrups), methocarbamol, and reserpine.

Medicines that can decrease 5-HIAA measurements include heparin, isoniazid, levodopa, monoamine oxidase inhibitors, methenamine, methyldopa, phenothiazines, and tricyclic antidepressants.

You will be told not to eat certain foods for 3 days before the test. Foods that can interfere with 5-HIAA measurements include plums, pineapples, bananas, eggplant, tomatoes, avocados, and walnuts.

The test involves only normal urination, and there is no discomfort.

This test measures the level of 5-HIAA in the urine. It is often done to detect certain tumors in the digestive tract (carcinoid tumors) and to track the progress of a person with a carcinoid tumor.

The normal range is 2 to 9 mg/24h (10.4 to 46.8 µmol/24h).

Normal value ranges may vary slightly among different lab. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

Abnormal results may be due to:

• Tumors of the endocrine system or carcinoid tumors

There are no risks with this test.