Side Effects of Melatonin: What Are the Risks

Melatonin is a hormone and dietary supplement commonly used as a sleep aid.
This article reviews the potential side effects of melatonin supplements.
What is melatonin?
Melatonin is a neurohormone produced by the pineal glands in your brain, mainly at night.
It prepares your body for sleep and is sometimes called the “hormone of sleep” or “hormone of darkness.”
Melatonin supplements are frequently used as a sleep aid. They help you fall asleep, improve sleep quality, and increase sleep duration. However, they don’t appear to be as effective as many other sleep medications (1Trusted Source).

Sleep isn’t the only body function melatonin affects. This hormone also plays a role in your body’s antioxidant defenses and helps regulate blood pressure, body temperature, and cortisol levels, as well as sexual and immune function (2Trusted Source).
Its use is growing, raising concerns about its possible side effects.
Does melatonin have any side effects?
A few studies have investigated the safety of melatonin, but none have found any serious side effects. It also doesn’t seem to cause any dependence or withdrawal symptoms (6Trusted Source, 7Trusted Source).
Some medical professionals are concerned that it may reduce the natural production of melatonin in the body. However, short-term studies suggest no such effects (8Trusted Source, 9Trusted Source, 10Trusted Source).

Several studies have reported general symptoms, including dizziness, headache, nausea, and agitation.
Melatonin supplements are generally considered safe in the short term, even when taken in very high doses. However, more research on its long-term safety is needed, especially in children (11Trusted Source).
Use in children
Parents sometimes give melatonin supplements to children who have trouble falling asleep (12Trusted Source).
However, the Food and Drug Administration has neither approved its use nor evaluated its safety in children.

In Europe, melatonin supplements are a prescription-only medicine intended for adults. However, one Norwegian study found that their unapproved use in children was on the rise (5Trusted Source).
While there is no specific cause for concern, many experts are reluctant to recommend this supplement for children.
This reluctance stems in part from its wide-ranging effects, which are not completely understood. Children are also considered a sensitive group, as they are still growing and developing.
Long-term studies are needed before melatonin can be used with absolute safety in children (13Trusted Source).

Daytime sleepiness
As a sleep aid, melatonin supplements should be taken in the evening.
When taken at other times of the day, they may cause undesirable sleepiness. Keep in mind that sleepiness is technically not a side effect but rather their intended function (14Trusted Source, 15Trusted Source).

Other concerns
Several other concerns have been raised, but most have not been thoroughly researched:
• Interaction with sleeping pills. One study found that taking the sleep medication zolpidem along with melatonin worsened zolpidem’s adverse effects on memory and muscle performance (19Trusted Source).
• Decreased body temperature. Melatonin causes a slight drop in body temperature.
• Blood thinning. Melatonin may also reduce blood coagulation. As a result, you
should speak with your doctor before taking high doses of it if you also take warfarin or other blood thinners (21Trusted Source).