What Does Serotonin Do?

What is serotonin?

Serotonin is one of our many neurotransmitters. These are chemicals which help signals travel from one area of the brain to another. Serotonin is produced in the brain and the intestines. It is used only where it is produced, as it cannot cross the blood-brain barrier. So, the serotonin produced in the brain can only be used in the brain, and so on.

Most of our brain’s cells are influenced by serotonin, thus allowing it to influence a number of our brain’s functions. About 80-90% of our serotonin is found in the gastrointestinal tract, blood platelets, and central nervous system. This allows it to influence multiple bodily functions.

What are its functions?


  • Mood balance
  • Sexual desire
  • Sexual function
  • Appetite
  • Nausea (signaling the feeling)
  • Depression (consistently low levels are believed to contribute to it)
  • Anxiety (low levels)
  • Sleep
  • Memory (formation)
  • Learning (especially using mnemonics)


  • Regulation of breast milk production
  • Bone density (consistently high level can lead to osteoporosis)
  • Vasoconstriction
  • Blood clotting
  • Nausea (expelling gut irritant through diarrhea)
  • Smooth muscle constriction (notably in the intestines, arteries and veins, uterus, bladder, and respiratory tract)
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