Melatonin tells the body it's night. As a supplement it may help jet lag and some sleep-timing problems; effects on general insomnia are small.
Labels vary
Testing of US melatonin gummies found actual content ranged widely from the label.
Evidence & sources
Melatonin may help with jet lag and certain sleep-timing disorders; for insomnia the benefit appears small. Evidence: moderate. Known: Reviews of clinical trials. Unknown: Long-term safety data are limited. Source: NIH NCCIH, Melatonin: What You Need To Know (Current revision).
In a 2023 analysis of melatonin gummy products, most were inaccurately labeled, with actual melatonin ranging from 74% to 347% of the labeled amount. Evidence: limited. Known: Laboratory analysis of 25 products. Unknown: One market, one time point. Source: Cohen et al., JAMA, Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US (2023).