Melatonin works in concert with your body's circadian rhythm.
In simple terms, the circadian rhythm is your body's internal clock. They know when it's time to sleep, wake up, and eat.
Melatonin also helps regulate body temperature, blood pressure and hormone levels (study 5 , 6 ).
Melatonin levels increase in your body when it's dark outside, signaling your body that it's time to sleep (study 7 ).
It also binds to receptors in the body and can help you relax. For example, melatonin binds to receptors in the brain to reduce nerve activity. In the eyes, it may help lower levels of dopamine, a hormone that helps you stay awake (study 8 , 9 , 10 ).
Although the exact way in which melatonin helps induce sleep is unclear, there is evidence that these processes may help induce sleep.
Conversely, light suppresses melatonin production. That way your body knows it's time to wake up (study 11 ).
Because melatonin helps your body prepare for sleep, people who don't get enough of it at night can have a hard time falling asleep
There are many factors that can lead to low levels at night. Stress, smoking, too much light at night (including blue light), too little daylight during the day, shift work and aging affect melatonin production (study 12 , 13 , 14 , 15 ).
Taking a melatonin supplement can help smooth out low levels and normalize the internal clock.