You probably reach for it on nights when sleep will not come. A gummy, a tablet, a dissolvable strip. Most of us treat melatonin like a vitamin, not a medication.
A large preliminary study of nearly 131,000 adults with insomnia changes that picture. People who used melatonin for a year or more had about a 90 percent higher chance of developing heart failure over the next five years, compared with matched peers who did not.
The research was released by the American Heart Association and presented at its 2025 Scientific Sessions. It has not yet been peer reviewed.
What the numbers actually showed
In the long-term melatonin group, 4.6 percent developed heart failure over the five-year follow-up. In the matched non-user group, the rate was 2.7 percent.
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Users were also nearly twice as likely to die from any cause during that time. And they were about three and a half times more likely to be hospitalized for heart failure.
The study tracked 130,828 adults, average age around 56, with about six in ten women. Half had at least a year of melatonin on their medical record. The other half, matched for age, sex and health profile, had none.
Why experts call this a signal and not a verdict
The researchers were clear about what the data can and cannot do.
"Melatonin supplements may not be as harmless as commonly assumed. If our study is confirmed, this could affect how doctors counsel patients about sleep aids," said Ekenedilichukwu Nnadi, M.D., chief resident in internal medicine at SUNY Downstate in Brooklyn.
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The study is observational. It cannot prove melatonin caused the heart problems. One big caveat is that insomnia itself raises heart failure risk, and people who take melatonin for a year tend to be those with the worst sleep problems to begin with.
That means part of the signal may belong to the sleep problem, not the pill.
A separate analysis published in the journal Open Heart in May 2026 looked at NHANES data from more than 50,000 US adults. After adjusting for other risk factors, recent melatonin use was not significantly linked to heart failure or cardiovascular disease.
The two studies measured different things. The mismatch is why the heart association's signal is still being treated as preliminary rather than settled science.
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What this means for you tonight
Short-term melatonin for jet lag or a few restless weeks was not what the study looked at. The signal appeared only in people with a year or more of continuous use.
If that describes you, the researchers' message is to raise it with your doctor rather than quit on your own. Chronic insomnia itself carries heart risks and needs its own treatment plan.
Melatonin is sold over the counter in the United States and shows up in sleep gummies, so long-term use is often invisible to a doctor's chart. Writing down how long you have taken it, and at what dose, is useful information to bring to that visit.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.