Urine Serotonin Level Test

This test measures the level of serotonin (5-hydroxytryptamine) in a urine sample, usually a 24-hour sample. A small portion of the serotonin produced in the body is excreted unchanged (unmetabolized) in the urine. This test is less sensitive and specific than measuring serotonin's main metabolite, 5-hydroxyindoleacetic acid (5-HIAA), in urine, but it may sometimes be used as a supplementary test in the evaluation of neuroendocrine tumors (NETs), particularly carcinoid tumors.