Research into a popular sleep aid has some scientists concerned about long-term use.
A recent analysis of adults with insomnia, which has not yet been peer-reviewed, found that people who took melatonin for more than a year had a greater risk of heart disease.
Among more than 130,000 adults in multiple countries, those who took melatonin long-term had an 89% higher risk of developing heart failure within five years and were twice as likely to die from any cause compared with those who did not take melatonin.
Watch the clip below for a summary of the findings:
These findings are preliminary and do not change current health recommendations. They don’t necessarily mean that melatonin — the fourth most popular natural product taken by U.S. adults — is causing dangerous effects.
The results do suggest that further research into the long-term use of melatonin is needed to ensure its safety.
Melatonin is generally considered safe and well-tolerated for short-term use in people who are not pregnant or breastfeeding. This means approximately 1 to 2 months.
There has been limited research on the effects of supplements since, and some researchers believe this situation should be corrected, especially as supplements become more popular.
The study was presented last November at the American Heart Association’s Scientific Sessions.
“Melatonin supplements may not be as harmless as commonly believed,” Ekenedilichukwu Nnadi, a medical scientist at SUNY Downstate/Kings County Primary Care Center, said at the time.
“If our study is confirmed, this could have implications for how doctors advise patients about sleep aids.”
Melatonin supplements replicate the hormone naturally produced by the brain, helping to keep the body’s internal clock ticking. Taking this alternative at the end of the day can help some people fall asleep and stay asleep.
In the United States and many other countries, melatonin supplements are available over the counter, which means patients can take them without medical guidance or supervision of dosage or length of use.
While some research suggests long-term use of melatonin is safe, comprehensive research is lacking.
Among other countries, a recent analysis by Nnadi and colleagues in the United States looked at electronic health records for adults in the United States and the United Kingdom, where melatonin is only available by prescription.
A secondary analysis found that people who took melatonin for more than a year were almost 3.5 times more likely to be hospitalized for heart failure than those who didn’t take melatonin.
Additionally, the risk of death from any cause jumped from 4.3% to 7.8% between groups.
This study is concerning, but the findings should be treated with caution. There is an important limitation to the study’s methodology.
Participants were not surveyed about melatonin use. Their prescription records are used to determine who took what medication. This means that the control group (people who do not take melatonin) may include, for example, people in the United States who take melatonin without a prescription.
Carlos Egea, president of the Spanish Federation of Societies of Sleep Medicine, who was not involved in the study, noted the caveat in an expert reaction to the study. However, he still takes the study’s associations seriously.
“These findings challenge the perception of melatonin as a benign chronic therapy and only highlight the need for controlled, prospective trials to elucidate its safety,” Egea opined.
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Even in the short term, melatonin can come with drawbacks that many users are unaware of. For example, a series of non-fatal overdoses among children in Australia has raised questions about the safety of supplements in certain age groups.
Melatonin products may be based on natural hormones, but that doesn’t mean there are no risks.
The findings were presented at the American Heart Association’s Scientific Sessions.
An earlier version of this article was published in November 2025.
