Merck Manual

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Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Last full review/revision Jul 2020| Content last modified Jul 2020
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NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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Melatonin, a hormone produced by the pineal gland (located in the middle of the brain), regulates the sleep-wake cycle. Melatonin used in supplements is derived from animals but most is produced artificially. In some countries, melatonin is considered a drug and is regulated as such.

Medicinal claims

People use melatonin mostly to treat insomnia and to help minimize the effects of jet lag or of shift work. People who are traveling across time zones may take melatonin on the day or night of departure and for 2 to 4 nights after arrival. People who rotate work shifts may take melatonin before going to bed. Research is being conducted in using melatonin to resynchronize the sleep-wake cycle for people in the early phases of Alzheimer disease, as well as for seasonal affective disorder (feeling depressed during winter months).

Evidence suggests that melatonin supplements can affect the sleep-wake cycle. Melatonin supplements also may help certain people with symptoms of jet lag or insomnia.

Possible side effects

Headache and transient depression may occur. Melatonin may worsen existing depression. Whether melatonin is safe when used long-term is unknown. Melatonin is best taken under medical supervision. If animal sources are used, infections may occur, caused by animal tissue contamination.

Possible drug interactions

Melatonin may increase effects of warfarin, increasing risk of bleeding.

More Information

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