This year, about six million North Americans will take over-the-counter sleeping pills called melatonin. The percentage of people taking melatonin regularly has increased five-fold, from 0.4 percent in 1999 to 2.1 percent in 2017 (JAMA, 2022;327(5):483-485), even though the evidence that it helps people fall asleep is controversial (J Clin Sleep Med, 2017;13(2):307-349). In the last 10 years the prevalence of people taking melatonin doses exceeding the recommended 5mg per day has increased more than three and a half times. Because melatonin is sold as an over-the-counter dietary supplement, it is almost totally unregulated, and pills containing five times the listed dose have been found.
Melatonin supplements are usually safe when taken in the short term (J Gen Intern Med, Dec 2005;20(12):1151-8), but some people take doses higher than the 5mg/day recommended to help them fall asleep every night. Even at the recommended dose, melatonin pills can cause drowsiness, confusion, irritability, anxiety, depression, tremors, headaches, dizziness, nausea, stomach cramps, and low blood pressure (Complement Ther Med, 2019 Feb;42:65-81; Clin Drug Investig, Mar 2016;36(3):169-75). Although melatonin has not been shown to impair memory, it can reduce a person’s ability to solve problems (Neuroscience & Biobehavioral Reviews, Aug 2021;127:459-473).
Melatonin pills are widely advertised to help you fall asleep at night, but scientific studies showing its benefits are controversial. It may be safe to take melatonin pills for a short course of a few weeks, but long-term safety has not been established.