Melatonin is a popular supplement that many use to improve sleep. While melatonin has not been shown to directly improve sleep quality, melatonin can decrease the amount of time it takes to fall asleep and can decrease body temperature – both of which are important for increasing sleep time. Not all will respond to melatonin, so start with a low dose around 5mg or less and work your way up to find your sweet spot.
Reference: Buscemi, N., Vandermeer, B., Hooton, N., Pandya, R., Tjosvold, L., Hartling, L., … & Vohra, S. (2005). The efficacy and safety of exogenous melatonin for primary sleep disorders a meta-analysis. Journal of General Internal Medicine, 20(12), 1151-1158.