Melatonin is a hormone that your pineal gland makes naturally. It helps you fall asleep by calming your body before bed. Melatonin works closely with your body’s circadian rhythm to help prepare you for sleep. Melatonin levels rise at night in response to darkness and decrease in the morning in response to light. Melatonin may support eye health, ease tinnitus symptoms, treat acid reflux and GERD, and alleviate migraine attacks, but stronger evidence is needed for these uses (Healthline).