Melatonin is a natural hormone that regulates the human biological clock.
Where is it found?
Melatonin is produced by the pineal gland, located within the brain. Levels of melatonin in
the body fluctuate with the cycles of night and day. The highest melatonin levels are found at
night. Melatonin is present in foods only in trace amounts.
Melatonin has been used in
connection with the following conditions (refer to the individual
health concern for complete information):
Who is likely to be deficient?
Although elderly people often have difficulty sleeping1 and melatonin
supplements have been shown to improve sleep in the elderly,2 melatonin secretion
does not appear to decline in healthy older adults to a significant degree, despite many
preliminary reports to the contrary.3 Most of these preliminary studies failed to
verify that older subjects were healthy and not using drugs that suppress melatonin secretion
(e.g., aspirin, ibuprofen, beta-blockers). Routine replacement of melatonin in
elderly persons is, therefore, not recommended.
Adults with insomnia have been shown to
have lower melatonin levels.4 Frequent travelers and shift workers are also likely
to benefit from melatonin for the resynchronization of their sleep schedules,5
though a melatonin “deficiency” as such does not exist for these people. Patients
with heart disease have been reported to have
low melatonin levels, but whether this abnormality increases the risk of heart disease or
whether heart disease leads to the low melatonin level is not yet known.6 People
with schizophrenia were found to have low
melatonin output and experienced significantly improved sleep following melatonin replacement
How much is usually taken?
Normally, the body secretes melatonin for several hours per night—an effect best
duplicated with time-release supplements. Studies using timed-release melatonin for insomnia have reported good results.8 Many
doctors suggest 1–3 mg of melatonin taken one to two hours before bedtime. Studies with
people suffering from sarcoidosis or cancer
have used very high amounts of melatonin—typically 20 mg per night. Such levels should
never be taken without the supervision of a doctor. Melatonin should not be taken during the
Are there any side effects or interactions?
Melatonin is associated with few side effects. However, morning grogginess, undesired
drowsiness, sleepwalking, and disorientation have been reported. Researchers have hypothesized
that certain people should not use melatonin supplements, including pregnant or breast-feeding women, people with depression or schizophrenia, and those with autoimmune disease,
including lupus, at least until more is
In one study, administration of 3 mg per day of melatonin for three months resulted in a
marked decline in sperm counts and a decline in sperm quality in two of eight healthy young
men.11 In one of these two men, sperm count and quality became normal after
melatonin was discontinued. Although this was a small study, it raises the possibility that
long-term use of melatonin could lead to infertility.
In a group of children suffering from neurological disorders, 1–5 mg of melatonin per
night led to an increase in the rate of seizures despite the fact that sleep
improved.12 Until more is known, children with neurological conditions should take
melatonin only under medical supervision.
Many other side effects have been attributed to melatonin supplementation, including
inhibition of sex drive, severe headaches, abdominal cramps, and formation of rudimentary
breasts in men.13 14 However, these associations have not been supported
by solid evidence.15 16 17 18 Since none of these
claims have been well documented or independently confirmed, these problems may not have been
due to melatonin.
Though most research reports that melatonin improves the quality of sleep, at least one
trial has found that four of fifteen men given melatonin had their sleep patterns disturbed by
One case of painful gynecomastia (enlarged breasts) has been reported involving a
56-year-old man who had been suffering from amyotrophic lateral sclerosis (Lou Gehrig’s
disease), and was taking 1–2 mg melatonin per day for one and a half years.20
As the signs and symptoms disappeared after melatonin was discontinued, the authors of the
report suspected that melatonin caused this side effect.
According to a preliminary report, blood levels of melatonin may be elevated in women with
fibromyalgia.21 Data in this report
did not indicate toxicity from melatonin, nor did the report suggest that melatonin causes or
exacerbates the symptoms of fibromyalgia. It did suggest there is no current
rationale for melatonin supplementation in people with fibromyalgia.
One-time oral administration of 1 mg of melatonin to post-menopausal women reduced glucose tolerance and insulin sensitivity when tested 45 minutes after
administration.22 This finding suggests that people with diabetes should use melatonin with caution and only
under the supervision of a doctor.
Are there any drug
Certain medicines may interact with melatonin. Refer to drug interactions for a list of those medicines.
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gynecomastia. Neurology 1999;53:435–6 [letter].
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