This week, a series of headlines warned about the potential risks of taking the sleep supplement melatonin, saying new research had linked it to a 90 percent increase in heart failure.
The research is from an unpublished study set to be presented at the American Heart Association’s scientific conference in New Orleans next week. But sleep experts say it is not possible to draw conclusions about melatonin from its findings, noting some major limitations of the study — which has not been peer-reviewed — including the fact that it did not prove cause and effect.
A more likely explanation of the results, experts argued, is that insomnia itself — or a health condition that can cause insomnia, such as undiagnosed sleep apnea — could be to blame. In that case, melatonin would be an “innocent bystander,” said Dr. Sujay Kansagra, a sleep physician at Duke Health who was not involved in the study.
The study, he said, “left me with a lot more questions than answers.”
What did the study find?
Researchers analyzed international health records from more than 130,000 adults with insomnia, who were sorted into two groups: One group included people who took melatonin supplements for at least one year, and the other included those who had no record of taking melatonin.
The researchers, led by Ekenedilichukwu Nnadi, a chief medical resident in primary care and internal medicine at SUNY Downstate Health Sciences University in Brooklyn, then looked at the risk of heart failure — which occurs when the heart can’t pump enough blood to provide the body’s organs with oxygen — over the course of five years.
The risk of heart failure was 4.6 percent for those in the melatonin group, compared to 2.7 percent for those who had no record of taking melatonin. Put another way: People who took melatonin, the study suggested, had a 90 percent higher risk of heart failure. They were also more than 3.5 times as likely to be hospitalized for heart failure and were twice as likely to die of any cause.
Dr. Nnadi said that it made sense that these numbers would grab attention, given that melatonin is one of the most widely used sleep aids.
But, in his view, some of the headlines suggesting that melatonin itself caused heart failure are “a little more alarming than the data really support.”
“What we found was just an association, not proof of causation,” he said. “That distinction can be easily lost in translation.”
What were its limitations?
One of the study’s major drawbacks is that it only counted people with documented melatonin prescriptions. In the United Kingdom and several European Union countries, getting melatonin requires a prescription, but in the United States and some other countries, anyone can buy melatonin supplements over the counter without consulting a doctor.
This means that some of the participants in the study’s non-melatonin group may actually have been taking the supplements too, even if it wasn’t reported in their medical records. This muddies the comparison, said Dr. Andrew W. McHill, a sleep and circadian rhythm scientist at Oregon Health & Science University.
It also lacked information about melatonin dosage and insomnia severity, said Dr. Phyllis Zee, a sleep doctor and researcher at Northwestern Medicine who was not involved with the study. Both of these factors could affect heart risks. Dr. Kansagra also noted that the risk of heart failure was quite low in both groups.
To understand whether melatonin increases heart failure risks, researchers would need to conduct randomized controlled trials assigning people to receive either melatonin supplements or placebos, said Dr. Akinbolaji Akingbola, a sleep medicine physician at the University of Minnesota, who was also not involved in the study.
Dr. Nnadi acknowledged the need for further study. One of his goals in conducting the study, he said, was to drum up more research into over-the-counter supplements like melatonin.
He plans to submit the paper for review and publication in early 2026, he said.
What should you make of the findings?
The study has too many limitations to determine whether melatonin increases the risk of heart failure — or even affects the heart at all.
Still, experts agree it’s a good reminder of just how little we know about supplement safety. Melatonin supplements may mimic a hormone that your body makes naturally, but that doesn’t make them free of health risks, said Dr. Zee.
Taking melatonin can help you adjust to a new time zone or shift your sleep schedule, Dr. McHill said. But most sleep experts agree that melatonin is not an effective insomnia fix. The hormone works by signaling to your brain that bedtime is drawing near, not by directly inducing sleep. In many studies, it’s no more effective than a placebo.
“The problem is that we’re always looking for a silver bullet to help us sleep better,” he said. But the strategies that really work — like cognitive behavioral therapy for insomnia, establishing healthy sleep routines and avoiding caffeine and alcohol before bed — take much more work than swallowing a gummy.
Caroline Hopkins Legaspi is a Times reporter focusing on nutrition and sleep.
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