serotonin is a chemical that your body produces from an amino acid called tryptophan. It acts as a neurotransmitter, which means it carries signals between nerve cells in your brain and other parts of your body. serotonin affects many functions, such as mood, sleep, appetite, digestion, nausea, wound healing, bone health and sexual desire. serotonin levels that are too high or too low can cause problems for your physical and mental health .
