What Is Melatonin?

Hormone Has Role in Circadian Rhythms, Jet Lag, and Insomnia

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Melatonin is a naturally occurring hormone that may be effective in treating some sleep problems including jet lag, insomnia, and circadian-rhythm sleep disorders.

What Is Melatonin?

Melatonin is a hormone that is secreted by the pineal gland, which is in an area of the brain called the hypothalamus. Melatonin is produced from the amino acid called tryptophan and can be found in the blood as well as in the cerebrospinal fluid that bathes the brain and spinal cord.

As a hormone, it conveys signals to other organs and seems to help regulate the circadian rhythms of the body.

Melatonin’s Role in the Circadian Rhythm

The circadian rhythm is the body’s natural pattern of physiological and behavioral processes that are timed to a near 24-hour period. These processes include things like the sleep-wake cycle as well as variations in body temperature, blood pressure, and the release of hormones. Melatonin levels increase after the onset of darkness and peak in the middle of the night between 11pm and 3am. Melatonin seems to promote sleep and can influence the timing of the sleep period.

Melatonin to Treat Sleep Problems

Melatonin may be effective in treating circadian rhythm disorders in which the desire for sleep is disrupted in its timing, resulting in difficulty falling asleep or inappropriate sleepiness. There are many common conditions that may be helped, such as:

What Are Common Side Effects of Melatonin?

There are many potential side effects of any drug, including hormonal supplements like melatonin.

Although you would be unlikely to experience most side effects -- and you may not have any of them -- some that may commonly occur include:

  • Stomach cramps
  • Decreased alertness
  • Amnesia (memory loss)
  • Chest pain
  • Circadian rhythm disruption
  • Confusion
  • Cramping
  • Daytime fatigue
  • Transient depression
  • Diarrhea
  • Dizziness
  • Drowsiness
  • Hallucinations
  • Headache
  • Hormone changes
  • High blood sugars
  • Low blood pressure
  • Increase eye pressure
  • Irritability
  • Mood changes
  • Nausea
  • Vomiting
  • Paranoia
  • Pruritus (itchy skin)
  • Seizures
  • Tachycardia (rapid heart rate)
  • Taste disturbance

Melatonin is not regulated as a drug and is available over-the-counter, but you should consult with your doctor to ensure that it is appropriate and safe to use to treat your sleeping difficulties.


Brzezinski, A et al. "Effects of exogenous melatonin on sleep: a meta-analysis." Sleep Med Rev 2005;9:41.

"Melatonin." Epocrates Rx Pro. Version 3.3, 2010. Epocrates, Inc. San Mateo, California.

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