What Is Melatonin and How Does It Work?

Melatonin is a hormone made by the brain, primarily in response to darkness. It plays a central role in regulating your circadian rhythm—your body’s internal 24-hour clock—and helps signal when it is time to sleep. Exposure to light at night can interfere with the body’s natural production of melatonin.

Beyond its role in sleep regulation, melatonin may influence other bodily processes. Researchers continue to study these potential effects, but many of them are not yet fully understood.

Melatonin supplements are available in several forms. While they can be derived from animals or microorganisms, most products are manufactured synthetically. The information below focuses on melatonin as a dietary supplement.

What Are the Health Benefits of Taking Melatonin?

Melatonin supplements have been studied for a variety of health concerns. Evidence suggests they may be helpful for jet lag, delayed sleep-wake phase disorder, certain sleep problems in children, and anxiety related to surgery.

Jet Lag

Jet lag can occur after traveling across multiple time zones. Symptoms may include disrupted sleep, daytime fatigue, difficulty concentrating, and digestive discomfort.

Research reviews indicate that melatonin supplements may reduce symptoms of jet lag.

• Four studies involving 142 travelers found that melatonin improved overall jet lag symptoms after eastward flights compared to a placebo. Another study of 234 travelers suggested that melatonin may improve sleep quality after eastward travel, though the evidence was limited.

• Two studies including 90 travelers reported that melatonin helped reduce jet lag symptoms following westward flights.

Delayed Sleep-Wake Phase Disorder (DSWPD)

Individuals with DSWPD have difficulty falling asleep at conventional times and struggle to wake up in the morning. They often cannot fall asleep until very late at night and prefer waking later in the day.

Melatonin supplements appear to help some people with DSWPD fall asleep earlier, though questions remain about long-term benefits and risks.

• In 2015, a professional sleep organization issued a cautious recommendation supporting timed melatonin use for DSWPD, noting uncertainty about the balance of benefits and harms.

• A 2016 review of two small studies (52 participants) found that melatonin shortened the time needed to fall asleep by about 22 minutes compared to placebo.

• A 2018 trial of 307 participants found that taking melatonin one hour before the desired bedtime, combined with a fixed sleep schedule, led to falling asleep about 34 minutes earlier and improved early-night sleep and daytime performance.

Some Sleep Disorders in Children

Sleep disturbances in children can affect mood, behavior, learning, and quality of life. Children with conditions such as ADHD, autism spectrum disorder (ASD), asthma, or atopic dermatitis are more likely to experience sleep difficulties.

Behavioral approaches—such as establishing consistent bedtime routines and educating parents—are typically recommended first. Medication may be considered when needed.

• A 2019 review of 18 studies involving 1,021 children found that short-term melatonin use improved how quickly children fell asleep and increased total sleep time. However, effects on behavior and daytime functioning were unclear.

The review reported the following short-term improvements:

• Children with ASD fell asleep 37 minutes earlier and slept 48 minutes longer.

• Children with ADHD fell asleep 20 minutes earlier and slept 33 minutes longer.

• Children with atopic dermatitis fell asleep 6.8 minutes earlier and slept 35 minutes longer.

• Children with chronic sleep-onset insomnia fell asleep 24 minutes earlier and slept 25 minutes longer.

There is limited information about optimal dosing, timing, and long-term safety in children. Because melatonin is a hormone, concerns exist about possible effects on puberty, menstrual cycles, and prolactin levels, though these effects have not been clearly established.

Consult a health care provider before giving melatonin to a child.

Anxiety Before and After Surgery

Up to 80 percent of patients experience anxiety before or after surgery.

Melatonin may help reduce preoperative anxiety, though its effects after surgery are less certain.

• A 2015 review of 12 studies (774 participants) found strong evidence that melatonin reduced anxiety before surgery compared to placebo. It may be comparable to standard anti-anxiety medication. Results for postoperative anxiety were mixed.

Is Melatonin Helpful for Preventing or Treating COVID-19?

Research on melatonin’s potential role in COVID-19 is still in early stages. Although some clinical trials are underway, there is currently insufficient evidence to determine whether melatonin is effective for prevention or treatment.

Does Melatonin Help With Cancer Symptoms?

Small studies have explored melatonin’s role in easing cancer-related symptoms or treatment side effects, but findings have been inconsistent.

Unproven supplements should not replace standard cancer treatments. Some supplements may also interact with cancer therapies. Anyone diagnosed with cancer should speak with their health care provider before using melatonin or other complementary approaches.

Can Melatonin Help With Insomnia?

Insomnia involves difficulty falling asleep, staying asleep, or both. When symptoms persist for a month or longer, it is considered chronic insomnia.

Clinical guidelines state that there is not enough strong evidence to recommend melatonin for chronic insomnia. Cognitive behavioral therapy for insomnia (CBT-I) is recommended as the first-line treatment.

Does Melatonin Work for Shift Workers?

Night shift workers often struggle with sleepiness during work hours and difficulty sleeping during the day.

Research findings are limited and inconclusive.

• One review of seven studies (263 participants) suggested melatonin might increase daytime sleep by about 24 minutes, though other sleep measures did not significantly improve. The evidence was low quality.

• Another review of eight studies (300 participants) found inconsistent results and did not make specific recommendations for melatonin use in shift workers.

Is It Safe to Take Melatonin?

Short-term melatonin use appears safe for most people. However, information about long-term safety—especially at higher doses—is limited.

Additional considerations include:

Interactions With Medicines

• People taking medications should consult a health care provider before using melatonin. Those with epilepsy or who take blood thinners should use melatonin under medical supervision.

Possible Allergic Reaction Risk

• Allergic reactions to melatonin supplements are possible.

Safety Concerns for Pregnant and Breastfeeding Women

• There is limited research on melatonin use during pregnancy or breastfeeding.

Safety Concerns for Older Adults

• Guidelines advise against melatonin use in people with dementia.

• Older adults may experience prolonged effects, leading to daytime drowsiness.

Melatonin Is Regulated as a Dietary Supplement

• In the United States, melatonin is regulated as a dietary supplement, meaning oversight is less strict than for prescription or over-the-counter medications.

Products May Not Contain What’s Listed on the Label

• Some products contain amounts of melatonin that differ from label claims. A 2017 study of 31 supplements found significant variation, and 26 percent contained serotonin, which can be harmful at certain levels.

Is Melatonin Safe for Children?

In addition to the concerns noted above, special considerations apply to children.

• Parents should consult a health care provider before giving melatonin to children.

• A 2023 study found that many melatonin gummy products were inaccurately labeled, with actual melatonin content ranging from far below to more than three times the listed amount.

• Safe storage is essential. From 2019 to 2022, an estimated 11,000 emergency department visits involved unsupervised melatonin ingestion by children age 5 and younger, often involving flavored gummies.

• Reports to poison control centers involving individuals age 19 and younger rose sharply between 2012 and 2021. Hospitalizations and serious outcomes also increased, particularly among teenagers with intentional overdoses and young children with accidental ingestion.

More Information

• Most poison control calls involved children age 5 and younger who accidentally consumed melatonin at home.

• The majority of cases did not result in symptoms. When symptoms occurred, they most often involved the digestive system, cardiovascular system, or central nervous system.

• Some hospitalized cases required intensive care, and a small number required mechanical ventilation. Two deaths in children under age 2 were reported, though the exact cause was unclear.

Short-term use of melatonin at typical doses appears safe for many children, but long-term effects are not well studied. Reported side effects in children are generally mild and may include:

• Drowsiness

• Increased urination or bedwetting

• Headache

• Dizziness

• Agitation

What Are the Side Effects of Melatonin?

Short-term studies in adults and surgical patients report mostly mild side effects, including:

• Headache

• Dizziness

• Nausea

• Sleepiness

The long-term side effects of melatonin supplementation remain uncertain.

Tips To Consider

• Dietary supplements are regulated differently from prescription and over-the-counter medications.

• Supplements may interact with medications or pose risks for people with certain medical conditions or those preparing for surgery.

• Pregnant or breastfeeding individuals should consult a health care provider before using melatonin.

• Always follow label instructions. “Natural” does not necessarily mean “safe.”

• Discuss any complementary health approaches with your health care providers to make informed, coordinated decisions.

For More Information

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information about complementary and integrative health approaches and related research. It does not offer medical advice, treatment recommendations, or referrals.

Know the Science

Educational resources are available to help consumers understand scientific research, clinical studies, and how to interpret health information.

PubMed®

A database of scientific and medical journal citations and summaries maintained by the National Library of Medicine.

NIH Clinical Research Trials and You

Information about clinical trials, their purpose, and how to participate.

National Heart, Lung, and Blood Institute (NHLBI)

Provides information about heart, lung, blood, and sleep disorders for patients and professionals.

Key References

A selection of scientific studies and clinical guidelines supports the information presented in this article, including research on sleep disorders, pediatric use, safety, and melatonin’s potential role in various health conditions.

Other References

Additional peer-reviewed articles and systematic reviews have examined melatonin’s clinical applications, safety profile, and biological effects.

Acknowledgments

This content is intended for educational purposes and should not replace professional medical advice. Always consult a qualified health care provider regarding treatment decisions.