Blood Serotonin Level Test

This test measures the concentration of serotonin (5-hydroxytryptamine or 5-HT) in serum or blood plasma. Serotonin is a neurotransmitter and hormone produced primarily by certain cells in the intestine (enterococcal cells) and to a lesser extent by platelets and the central nervous system. Measuring serotonin in the blood is mainly used as an adjunct (not a primary) marker for the diagnosis and monitoring of carcinoid syndrome caused by serotonin-producing carcinoid tumors.