A new study presented at the American Heart Association’s 2025 Scientific Sessions links long-term melatonin use in people with insomnia to a higher risk of heart failure. The findings challenge the common view that melatonin is a safe and natural sleep aid.
Researchers reviewed five years of health records for more than 130,000 adults who had been diagnosed with insomnia and had taken melatonin for at least a year. They compared their cardiovascular disease risk with that of similar patients who did not take the supplement.
Key findings
About 4.6 percent of long-term melatonin users developed heart failure, compared with 2.7 percent of non-users. That represents a nearly 90 percent higher risk. Long-term users were more than three times as likely to be hospitalized for heart failure: 19 percent versus 6.6 percent. Over the five-year period, nearly twice as many melatonin users died from any cause compared with non-users: 7.8 percent versus 4.3 percent.
“Melatonin supplements are widely thought of as a safe and ‘natural’ option to support better sleep, so it was striking to see such consistent and significant increases in serious health outcomes, even after balancing for many other risk factors,” said Ekenedilichukwu Nnadi, M.D., lead author of the study, in a statement.
The researchers stress that the results show an association, not proof of causation. Nevertheless, the consistency of the findings gives reason for caution.
What the findings mean for melatonin use
“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,” Nnadi said.
Several factors add nuance to the results. Chronic insomnia itself is independently linked to a higher risk of heart problems, including heart failure. People who rely on melatonin for more than a year may have more severe sleep disruptions, and using melatonin could be a marker of poor sleep health rather than a direct cause of heart disease.
Also, the study identified “melatonin users” based on prescription records. In many countries melatonin is a prescription drug, but in the United States it is sold over the counter. This means that many U.S. users may have been incorrectly counted as non-users, making it harder to measure the true difference.
Experts have long warned about unknown safety effects of melatonin. This study adds to those concerns. While short-term use at appropriate doses may help with occasional jet lag, the findings suggest melatonin is not suitable for nightly long-term use.
Alternatives for better sleep
For people with insomnia or general sleep difficulties, many options exist besides melatonin. Improving sleep hygiene — such as avoiding alcohol late at night, keeping the bedroom dark and cool, and reducing screen time — is a good starting point. For those who want a supplement, magnesium is a recommended alternative.
Magnesium is an essential mineral that many people, about 43 percent, do not get enough of through diet alone. Low magnesium levels can contribute to heightened stress, muscle tightness, restless sleep, and mood changes. Taking magnesium before bed may help ease the body and mind into relaxation. It works in part by activating receptors for GABA, a neurotransmitter that calms an overactive nervous system and promotes sleep.
Many sleep supplements are available, and magnesium-based options are often considered the best choice.
The takeaway
Though preliminary, the study suggests that nightly long-term use of melatonin may carry more risks than previously thought. Short-term use, good sleep habits, and supportive nutrients such as magnesium remain safer ways to improve sleep naturally.
