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Medically reviewed by Last updated on Dec 24, 2018.

What is Melatonin?

Melatonin is a hormone produced by the pineal gland in all vertebrates. It is also produced in the eye, GI tract, bone, skin, lymphocytes, platelets, and thymus. Melatonin secretion is inhibited by environmental light and stimulated by darkness. Secretion starts at 9 PM and peaks between 2 and 4 AM at approximately 200 pg/mL. The duration of melatonin production varies throughout the year, with shorter periods occurring in the summer months and longer periods occurring in the winter months. Nighttime secretion of melatonin is highest in children and decreases with age. In addition to being produced in vertebrates, melatonin is also found in plants, bacteria, various single-celled organisms, and invertebrates.

Melatonin is a dietary supplement and has not been approved by the US Food and Drug Administration. It is derived as a synthetic product or from animal pineal tissue. Use of the tissue-derived product is discouraged because of a risk of contamination or viral transmission. Melatonin is also present in large quantities in some plants.

Melatonin is being studied in depression and sleep disorders.

Scientific Name(s)

Melatonin, N-acetyl-5-methoxytryptamine

Common Name(s)


A prolonged-release form of melatonin is commercially available (Circadin).

What is it used for?

Traditional/Ethnobotanical uses

Early animal studies of melatonin in the mid-1960s revealed its ability to affect sexual function, skin color, and other mammalian functions. Early studies showed that daily variations in estrogen secretion in rats could be regulated by changes in melatonin synthesis and release, induced by the daily cycle of light and dark. Continual darkness depresses the estrous cycle. Studies in the 1990s led to widely expanded uses of melatonin, including easing insomnia, combating jet lag, preventing pregnancy (in large doses), protecting cells from free-radical damage, boosting the immune system, preventing cancer, and extending life.

General uses

A large amount of clinical trial data exists to support melatonin's role in reducing many sleep-related disorders in adults and children. Evidence is less clear for improvements in sleep duration or quality. Clinical trial data suggest that melatonin may increase survival rates in solid tumor cancers and decrease the adverse effects of chemotherapy. Increased healing rates in stomach ulcers have been found in a small number of studies when melatonin was used as add-on therapy. Treatment of infertility, high-blood pressure, anxiety, headache, and ringing in the ears has also been studied.

What is the recommended dosage?

Adjunctive therapy in cancer

Dosages of up to 20 mg/day have been used in trials.


3 to 5 mg daily in the evening over 4 weeks. Independent studies have not yet clarified the effectiveness of sustained-release preparations.

Jet lag

In general, lower doses (0.5 to 2 mg) preflight and higher doses (5 mg) postflight over a period of up to 4 days appear to be adequate.


Melatonin 2 to 5 mg has been used in children.


Until it is studied more thoroughly, melatonin should not be used by patients with an autoimmune disease.


Information regarding safety and efficacy in pregnancy and lactation is lacking.


Melatonin has been used in many conditions in addition to standard therapy with few reports of interactions.

Side Effects

Possible adverse reactions include depression, dizziness, inability to control urination, excessive daytime sleepiness, headache, nausea, and short-term depression. Drowsiness may be experienced within 30 minutes after taking melatonin and may persist for approximately 1 hour; as a result, melatonin may affect driving ability.


Studies are limited. There is little or no evidence of major toxicities with melatonin, even at high doses.


1. Melatonin. Review of Natural Products. Facts & Comparisons [database online]. St. Louis, MO: Wolters Kluwer Health Inc; February 2013.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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