5HTP stands for 5-hydroxytryptamine, a chemical compound that occurs naturally in the body. It is synthesized from tryptophan and is a precursor to serotonin, a neurotransmitter involved in many important brain functions. 5HTP is used as a supplement to increase serotonin levels and treat various health problems, including depression, anxiety, insomnia, and obesity. 5HTP supplements are usually made from a plant called Griffonia simplicifolia, which contains high concentrations of the compound. 5HTP supplements are usually taken as capsules or oral tablets.