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Home / Melatonin and Sleep / Melatonin Side Effects

Melatonin Side Effects

Jay Summer

Written by

Jay Summer, Staff Writer

Dr. Nilong Vyas

Medically Reviewed by

Dr. Nilong Vyas, Pediatrician

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Melatonin is a naturally occurring hormone. As the sun goes down and darkness sets in, the brain releases melatonin to promote sleep.

Synthetic or lab-made versions of melatonin are widely available as a sleep aid supplement. For people who have trouble falling asleep, taking melatonin before bedtime may help. Melatonin may also reduce jet lag and help treat circadian rhythm disruptions.

In the last two decades, melatonin usage has increased modestly but consistently among adults in the United States. As with any supplement or medication, safety is a top priority. Before taking melatonin, it is important to understand the possible adverse reactions and potential interactions with other drugs

Potential Side Effects of Melatonin

Adverse reactions to melatonin tend to be relatively rare and mild, with the most common side effects including:

  • Headache
  • Daytime sleepiness
  • Dizziness
  • Nausea

Much of the research has focused on the effects of taking melatonin for only a short period of time. Higher quality research is still needed, but the available evidence suggests that melatonin is generally safe for short-term use of up to three months.

Adverse effects tend to occur with higher doses or with supplements designed to provide extended release of melatonin. Aside from headache, dizziness, nausea, and daytime sleepiness, some studies have reported side effects like vivid dreams, nightmares, stomach cramps, irritable mood, and brief bouts of depression.

Melatonin can remain active in the body for longer periods of time in older adults. This means that melatonin may be more likely to cause sleepiness the next day when it is taken by older people.

People taking melatonin do not appear to build up a tolerance to the supplement, but additional research is needed.

One preliminary study found that long-term melatonin use may be associated with reduced sperm quality in men and people with a prostate. Further research is necessary to investigate this and any other potential effects of using melatonin supplements over a long period of time.

Side Effects in Children

Melatonin is generally considered safe for short-term use in children, but more studies are required to better understand its long-term effects in young people.

In the limited research to date, the potential short-term side effects of melatonin in children appear to be mild. These may include:

  • Headache
  • Dizziness
  • Drowsiness
  • Agitation
  • Increased nighttime urination or bedwetting

The long-term effects of melatonin in children are less clear. Some researchers have concerns that melatonin could disrupt normal hormone levels and interfere with puberty. But studies monitoring melatonin use for up to four years have not found a significant risk for kids.

Parents and caregivers should keep in mind that while melatonin may help with certain sleep disorders, medical professionals do not recommend melatonin as a general sleep aid for children or adolescents.

There is evidence that melatonin can be helpful for children experiencing insomnia or a delayed circadian rhythm. But parents and caregivers should avoid using melatonin to induce sleep in otherwise healthy kids or teenagers. Experts suggest starting with lifestyle and behavioral changes prior to trying melatonin or medications.

Consulting with a pediatrician can provide the most direct guidance on the benefits and risks of melatonin use for any specific child’s situation.

Melatonin and Pregnancy

People who are pregnant or breastfeeding may want to avoid taking melatonin because there is a lack of evidence about its safety in these situations.

Anyone who is pregnant or nursing and experiencing sleep difficulties should talk with their doctor before taking melatonin.

The side effects of melatonin are also generally unknown for people trying to become pregnant. There is insufficient evidence about melatonin’s impact on conception, so some experts recommend avoiding melatonin supplements as a precaution when trying to become pregnant.

 

Side Effects and Melatonin Dosage

The appropriate melatonin dosage can vary depending on a person’s age and symptoms. but typical doses range from 1 to 2 milligrams for preschool-aged children, 2 to 3 milligrams for school-aged children, and up to 5 milligrams for teens and adults.

The dose of melatonin may influence the potential side effects. Adverse effects may be more likely with higher doses.

That is why a “less is more” approach can be helpful when trying melatonin, especially in children. A low dose can be used initially and slowly increased as needed. Even in adults, doses as low as 1 milligram or less may be effective for certain sleep problems.

For those with trouble falling asleep, taking melatonin a few hours before bed may be beneficial. And people who struggle to stay asleep at night may want to consider an extended-release melatonin supplement. Extended-release melatonin metabolizes more slowly in the body and may help reduce nighttime awakenings.

Melatonin Labeling Accuracy

One major concern when it comes to melatonin side effects and dosing is the accuracy of supplement product labels.

The FDA classifies melatonin a dietary supplement. Dietary supplements are not as tightly regulated as prescription and over-the-counter medications. One study examined 31 different melatonin supplements and found the actual concentrations of melatonin often differed significantly from what was listed on the product labels.

To ensure accurate melatonin dosing and to reduce the risk of adverse effects, shop for supplements from reputable manufacturers whose products have been evaluated for quality control by independent organizations. Melatonin can also degrade over time, so make sure to check the expiration date on the bottle.

Is Melatonin Safe?

Melatonin is generally considered to be safe for short-term use, but there may be safety concerns for people with certain pre-existing conditions or those taking specific medications.

Melatonin is not right for everyone, and certain people should be cautious and speak with a doctor before taking melatonin supplements.

  • People on dialysis or with liver problems: People with reduced kidney or liver function may not be able to metabolize melatonin and have a higher risk of adverse side effects.
  • Those who are pregnant or breastfeeding: There is not enough evidence to guarantee the safety of melatonin use in people who are pregnant, breastfeeding, or trying to conceive.
  • Older adults with dementia: The American Academy of Sleep Medicine recommends that older people with dementia avoid taking melatonin. For these individuals, the potential safety risks of melatonin likely outweigh the possible benefits.
  • People experiencing depression: Melatonin may cause symptoms of depression or make existing symptoms worse in some people.
  • People with immune issues: Melatonin can activate certain parts of the immune system. While the significance of this effect is still unclear, people with autoimmune disorders or who are taking immune-suppressing medications may want to avoid using melatonin.

In addition, melatonin can interact with certain medications. One example is warfarin, a drug used to prevent blood clotting. Melatonin may increase the effect of warfarin, thereby increasing the risk of bruising and excess bleeding. Anyone taking one or more prescription medications should talk with a doctor before trying melatonin.

Melatonin Overdose

Melatonin can cause adverse effects at higher doses, but it is unlikely to cause a lethal overdose.

In adults, higher doses may cause uncomfortable side effects such as headache and nausea.

Melatonin overdose in children is a growing concern with increasing hospitalizations in recent years. However, this increase was largely due to accidental ingestion of melatonin in children younger than 5 years old. Appropriate doses of melatonin for short-term use remains generally safe for children, but parents and caregivers should practice safe storage of all medications and supplements around the house.

It is also important to keep in mind that some melatonin supplements may not be accurately labeled. This increases the risk of taking a higher dose than intended. If you have any concerns about having taken too much melatonin, contact poison control for immediate and free expert advice.

When to Consider Other Sleep Aids

Melatonin may not be safe or effective for everyone. In general, melatonin should be avoided as a sleep aid for people who are pregnant or nursing as well as people with certain health conditions.

People who try melatonin and do not find that their sleep improves or who have unwanted side effects may want to consider a different sleep aid. While melatonin has shown promise in helping with some sleep problems, experts do not recommend it as an initial treatment for insomnia.

There are a wide range of other dietary supplements marketed as sleep aids, but few have been proven effective in research trials. The FDA has approved a number of over-the-counter drugs as sleep aids. People experiencing stubborn sleep issues can also speak with their primary care physician about other effective therapies and prescription sleep medications.

In addition, taking a sleep aid may be unnecessary for many people. Other types of non-medical treatments including sleep-directed therapy can be effective in resolving sleep problems without the need to use prescription drugs or other sleep aids.

When to Talk to Your Doctor

Anyone who has a preexisting health condition or is taking a prescription medication should consult with their doctor before trying melatonin. And anyone experiencing an adverse reaction from melatonin should stop taking the supplement and contact their doctor.

It is always a good idea to make a doctor aware before adding a new supplement to a health regimen. A doctor or pharmacist may be able to help with the timing or dosage of melatonin and discuss its benefits and risks.

Although melatonin supplements are easily found in stores or online as a dietary supplement, it is important to try to find a reputable brand, follow the instructions on the label, and follow up with the doctor if any negative side effects occur.

Seeking the advice of a doctor is also recommended if sleep problems persist over several weeks or months, including after taking melatonin. Melatonin can be helpful for certain sleep issues, but it is not a treatment for other sleep disorders, including obstructive sleep apnea. A doctor can review a person’s symptoms, provide an informed diagnosis and treatment plan, and offer a referral to a sleep specialist if needed.

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About Our Editorial Team

author
Jay Summer

Staff Writer

Jay Summer is a health content writer and editor. She holds a B.S. in psychology and master's degrees in writing and public policy.

author
Dr. Nilong Vyas

Pediatrician

MD

Dr. Vyas is a pediatrician and founder of Sleepless in NOLA. She specializes in helping parents establish healthy sleep habits for children.

References

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