I usually sleep about 6 hours and feel not always well rested. Do I need to supplement melatonin to improve my sleep?

Melatonin is unlikely to meaningfully improve your total sleep, so supplementation may not be worthwhile for a non-elderly adult. It can signal that it is time for sleep, but does not drive sleep through the night; a meta-analysis found an average increase of just 3.9 minutes of sleep and 2.2% in sleep efficiency among healthy adults. 1

• Sleepiness versus staying asleep: Melatonin may help you fall asleep, but it may not help you stay asleep; some people wake after three to five hours and have difficulty falling back asleep. 2
• Dose and product concerns: Common supplement doses can be many times higher than the body’s natural melatonin levels. High doses may affect other hormone systems, and tested products have shown substantial differences between the amount on the label and the amount in the supplement. 3 4
• Older adults: Melatonin may be a more reasonable use case for older adults, particularly those with insomnia, because age-related changes in the pineal gland can reduce melatonin release. 5
• Alternatives: Prioritize behavioral habits before supplements, including getting morning sunlight and keeping the bedroom cool; falling and staying asleep is easier in a room that is too cold than too hot. 6 7

Feeling unrefreshed after six hours is not, by itself, evidence that melatonin is the answer. 8