Medical Definition of Melatonin
Melatonin: A hormone that is produced by the pineal gland and is intimately involved in regulating the sleeping and waking cycles, among other processes. Some people who have chronic insomnia use melatonin supplements. However, melatonin is not recommended for all patients with sleep problems, so one should consult a physician before taking it.
Last Editorial Review: 5/13/2016
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