Nov. 3, 2025, 5:00 AM ESTBy Erika EdwardsTaking melatonin for long periods of time could be a sign of underlying heart problems.Long-term use of the popular over-the-counter sleep aid has been linked to a higher risk of heart failure and early death in adults with insomnia, according to research released Monday.There’s no evidence that melatonin supplements themselves cause heart problems, the researchers said. But a need to take them on a regular basis to help with falling and staying asleep could be a signal that the body is experiencing cardiac issues.“Insomnia can increase blood pressure, stress hormones and inflammation,” said Dr. Ekenedilichukwu Nnadi, lead author of the new study and an internal medicine resident at SUNY Downstate/Kings County Primary Care in New York City.Nnadi and colleagues looked at five years of electronic health records from 130,828 adults, average age 56, finding that people who took melatonin regularly for at least a year were nearly twice as likely to develop heart failure compared to those who didn’t use the supplement, though the actual rates were relatively low: 4.6% of people in the melatonin group developed heart failure, compared to 2.7% among those who didn’t take melatonin.They were more than three times as likely to be hospitalized for the condition (19% versus 6.6%), and nearly twice as likely to die during the study period, compared to people who didn’t take melatonin regularly.It’s unclear, however, whether the data captured outcomes of all people in the U.S. who take melatonin long term. Researchers identified people as chronic users of melatonin based on medical records only — that is, if they’d been prescribed the supplement. In the U.S., the supplement is available over the counter and isn’t often reflected in medical records.“I caution people against drawing concrete conclusions based on this study alone,” said Dr. Nishant Shah, a preventive cardiologist at Duke University Medical Center in Durham, North Carolina, who wasn’t involved with the study. “But now that we have this observation, this is prime time to figure out whether there’s actually a direct association of harm with sleep agents. That would be practice-changing.”Nnadi’s research is scheduled to be presented in New Orleans at an upcoming meeting of the American Heart Association. It has not been published in a peer-reviewed journal.Heart failure occurs when the heart can’t pump enough oxygen-rich blood to the body’s organs for them to function properly. Nearly 7 million Americans have the condition, according to the Centers for Disease Control and Prevention.While the study found that long-term melatonin use was an indicator of potential heart problems — and not causing the problems itself — experts agreed more research is needed into the supplements’ possible side effects.“We have patients using all kinds of supplements without understanding the risks,” said Dr. Martha Gulati, a preventive cardiologist and the incoming director of the Davis Women’s Heart Center at Houston Methodist DeBakey Heart and Vascular Institute in Texas. “If there is harm from a supplement, it means the cost could be far more than simply expensive urine.” Gulati was not involved with the new study.Melatonin is a hormone made naturally by the body that helps regulate sleep and wake cycles. Synthetic versions, sold widely over the counter as dietary supplements, are marketed to help people fall asleep faster or overcome jet lag. Because supplements aren’t regulated by the Food and Drug Administration, doses and purity can vary widely among brands.Use of the supplement has increased in recent years. A 2022 Sleep Foundation survey found that up to 27% of U.S. adults take melatonin, as well as 4% of kids. The new study didn’t include children.People taking melatonin for sleep for more than a year should talk with their doctor, experts said.“People should be aware that it should not be taken chronically without a proper indication,” Marie-Pierre St-Onge, director of the Center of Excellence for Sleep & Circadian Research at Columbia University Irving Medical Center in New York, said in a press release. St-Onge was not involved with the new research.Erika EdwardsErika Edwards is a health and medical news writer and reporter for NBC News and “TODAY.”