Millions of people rely on melatonin as a natural, cheap sleep aid, but a new study suggests the over-the-counter supplement may be linked to an increased risk of heart problems.
The research—recently presented at the American Heart Association’s Scientific Sessions 2025 and not yet peer-reviewed—found that melatonin users had higher rates of heart failure, hospitalizations, and death compared with non-users.
Experts emphasized, however, that the study does not prove that melatonin causes these heart issues.
To better understand how melatonin might affect the heart, researchers recruited more than 130,000 adults—65,414 who took melatonin for at least a year and an equal number who didn’t. Over five years, they followed participants and tracked new heart failure diagnoses, heart-failure-related hospitalizations, and all-cause mortality.
Researchers found that melatonin users had higher rates across all categories:
- Heart failure: 4.6% of melatonin users (3,021 people) developed heart failure compared to 2.7% (1,797 people) from the control group—about a 90% higher risk.
- Hospitalizations: 19% of melatonin users (12,411 people) were hospitalized for heart failure versus 6.6% (4,309) of non-users, making them 3.5 times more likely to be hospitalized.
- All-cause mortality: Melatonin users were nearly twice as likely to die from any cause over the five-year period compared with those who did not take the supplement.
The study’s lead author, Ekenedilichukwu Nnadi, MD, chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, noted that the findings raise important questions.
“Melatonin supplements may not be as harmless as commonly assumed,” he said in a press release. “If our study is confirmed, this could affect how doctors counsel patients about sleep aids.”
Still, he and other experts said it’s far too soon to conclude that the supplement harms the heart.
Because the research hasn’t been published, more details about the study design and participant demographics are needed to better understand the implications, Abha Khandelwal, MD, an imaging cardiologist and clinical associate professor of cardiovascular medicine at Stanford Medicine who wasn’t involved with the research, told Health.
Joyce M. Oen-Hsiao, MD, FACC, a cardiologist and associate professor of cardiology at Yale Medicine who was also unaffiliated with the new study, added that the findings contrast with two decades of evidence suggesting melatonin may actually benefit people with heart failure.
However, she said the new study was not “designed in a way to prove that there is a direct relationship between melatonin use and increased heart failure.”
Other factors could explain the higher risk seen in melatonin users. People with insomnia often have other medical issues, like anxiety or depression, that can affect heart health, according to Oen-Hsiao. Those with chronic insomnia also tend to have higher rates of obesity, be older, or have hypertension, diabetes, or limited physical activity, Khandelwal added.
Again, there’s no solid evidence that melatonin causes heart problems or increases the chances of death. Still, there are plausible explanations for why it might, said Eman A. Hamad, MD, a cardiologist and the director of the Advanced Heart Failure & Transplant Program at Temple University Hospital.
Melatonin, a hormone produced by the brain, helps regulate the body’s circadian rhythm, which affects blood pressure, heart rate, and vascular tone. “Taking it chronically or in high, unregulated doses could disrupt those normal day–night patterns,” she told Health.
Hamad also pointed out that supplements in the U.S.—which are largely unregulated—often contain higher doses than what’s listed on the label. In the case of melatonin, she said, that could potentially “cause excessive drops in blood pressure or heart rate in sensitive individuals.”
Research has shown that melatonin can help reduce cholesterol, blood pressure, and inflammation in the arteries, Oen-Hsiao told Health. The supplement may also improve sleep for some people, and better sleep is consistently linked with lower stress and higher energy, she added.
With that in mind, you don’t need to ditch the melatonin just yet, Oen-Hsiao noted. Most people can safely take it at the recommended dose. Ideally, start with the lowest dose available and avoid taking it every night, she advised.
If you’re concerned about potential risks, Hamad recommended scheduling an appointment with your doctor. They can review your medical and family history, assess any underlying sleep disorders and risk factors, and determine if melatonin is right for you.
“To me, it’s a ‘proceed with caution’ finding,” she said of the new study. “Not a reason for panic, but a reason to reevaluate chronic, unsupervised melatonin use.”
