Laboratory Testing: What This Test Is, How It Is Performed, and How to Prepare

This test is a laboratory analysis that helps your healthcare provider screen for certain conditions, diagnose a health problem, or monitor how well a treatment plan is working by measuring specific substances in a sample taken from your body. Your doctor will use the results, along with your symptoms and medical history, to guide decisions about your care.

The 5-Hydroxyindoleacetate (5-HIAA) urine test measures the amount of 5-HIAA in your urine. 5-HIAA is a waste product created when your body breaks down serotonin, a hormone and neurotransmitter. This test is primarily used to detect and monitor carcinoid tumors, which are rare growths that can develop in various parts of the body and produce excess serotonin.

The test is usually performed by a trained healthcare professional who collects a small sample, such as blood, urine, or tissue, following standard clinical procedures. Most sample collections take only a few minutes. You may feel brief discomfort, such as a quick pinch or slight pressure, and the sample is then sent to a laboratory where specialists analyze it and report the results to your provider.

This test requires a 24-hour urine collection. You will be given a special container to collect all urine produced over a 24-hour period. It is important to keep the container refrigerated or in a cool place during collection. Follow your healthcare provider's instructions carefully to ensure accurate results.

Preparation depends on the type of test your provider has ordered. You may be asked to fast for a certain number of hours, avoid specific foods, drinks, or medications, or drink extra water beforehand. Tell your care team about all medicines, supplements, and allergies you have, follow any instructions they give you, and arrive on time so the sample can be collected properly and your results are as accurate as possible.

Before the test, avoid certain foods that can affect results, including bananas, avocados, plums, kiwis, pineapples, tomatoes, and walnuts. Also avoid medications such as antidepressants, cough syrups, and pain relievers. Your doctor will provide specific instructions about which medications to temporarily stop taking.