Can You Overdose On Melatonin?
In our latest question and answer, the pharmacist discusses whether or not it is possible to take too much, or "overdose" on melatonin.
Can you take too much melatonin at once or overdose?
According to toxicology studies, it appears unlikely that you can "overdose" on melatonin. Studies in rats have shown that the LD50 (i.e. amount of an ingested substance that kills 50 percent of a test sample) is 800 mg/kg. This would translate to a dose of over 36,000 mg for a 100 pound human!
Considering the usual dose of melatonin is 0.5 mg to 10 mg, overdosing doesn't seem possible. While human and animal studies certainly aren't directly comparable, it gives us a good idea of the relative safety of a medication.
In fact, according to multiple studies and published information about melatonin, it appears to be relatively safe for short term use.
- One large meta-analysis study concluded that evidence suggests that dosing melatonin for up to 3 months is considered safe
While overdosing with melatonin isn't likely, it certainly is possible that taking too high of a dose, or taking it for too long, could cause potential side effects and disruption of the normal circadian rhythm. Below, we discuss this in more detail.
Melatonin is a hormone that is naturally produced and secreted in the brain by the pineal gland. Melatonin production is stimulated by darkness and suppressed by light and is involved in the regulation of many different bodily functions. Perhaps the most well-known aspect of melatonin is the important role it plays in our bodies circadian rhythm. Additional functions of melatonin include:
Our bodies naturally produce melatonin but most supplements available over the counter are synthesized in the laboratory. Rarely, melatonin supplements are extracted and produced from an animal pineal gland. Various studies have been conducted in humans in regard to melatonin supplementation have shown shown that exogenous (i.e. not produced in the body) melatonin has hypnotic effects and can potentially help induce sleep in certain situations such as in those experiencing jet lag.
While melatonin is used for a wide variety of indications, usual dosages used for sleep are as follows:
Chronic fatigue syndrome
Melatonin 5 mg in the evening for 12 weeks has been studied and may be effective.
Delayed sleep phase syndrome (DSPS):
Melatonin 0.3 to 5 mg daily for up to 9 months has been studied and shown to be effective.
Studies on the use of melatonin have used a wide range of doses for the treatment of insomnia:
- Initial doses for the treatment of insomnia are generally between 0.5 mg and 3 mg at bedtime.
- Higher doses of 5 mg to 10 mg have been used for short periods of time (~1 week) when lower doses aren't effective.
- Doses for secondary insomnia (i.e insomnia due to other disease states such as schizophrenia and Alzheimers) range from 2 mg to 12 mg.
The most common doses of melatonin for jet lag range from 0.5 mg to 8 mg, taken at local bedtime on the day of arrival and continuing for 2 to 5 days thereafter. It should be noted that doses above 5 mg do not seem to be more effective than 5 mg doses, according to a few studies.
Insomnia In Children
While doses can range, studies show that 1 to 3 mg doses are the most commonly used for children.
Melatonin Side Effects
Melatonin is typically well tolerated, but has been reported to cause the following side effects in individuals:
There are some reports of melatonin causing a "daytime hangover effect" and reduced alertness. However, this is generally associated with unusually high doses (~50 mg) or if melatonin is not taken before bedtime.
Although melatonin in generally considered well tolerated and safe, more information is needed regarding the safety of long term use.
Long Term Melatonin SafetyIt is important to remember that melatonin is a hormone and long term use may affect other hormones in the body via bodily feedback systems. For example, One study noted that melatonin use over the long term could potentially affect male fertility. In addition, studies have theorized that long term melatonin use could adversely affect sexual development in children.
Lastly, long term use is also associated with possible desensitization to endogenous (i.e. naturally produced) melatonin, which could possibly disrupt sleep cycles over time.
As mentioned at the beginning of the article, acute overdoses appear extremely unlikely on melatonin. There are no reported overdose deaths of acute ingestion of melatonin. Case studies of individuals taking large amounts of melatonin in an attempt to overdose show that symptoms are relatively mild and associated hospital stays are uneventful.
This may be related to the fact that our bodies metabolize melatonin from supplements very quickly. Studies shows that the half-life (time it takes for our bodies to metabolize 50% of a drug) of melatonin is only 30 to 120 minutes, depending on the individual. The half-life isn't affected by high or low doses.
- It is unlikely that you are able to "overdose" while taking melatonin. Large doses have been used with no serious acute adverse effects.
- Short term use (less than 2 months) of melatonin is generally considered safe.
- More data is needed regarding long term use of melatonin, especially in children.
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