A new study presented at the American Heart Association’s 2025 Scientific Sessions suggests that people who take melatonin every night for a year or more may face a higher risk of heart failure. The research looked at health records from more than 130,000 adults in the United States who had been diagnosed with insomnia and had used melatonin for at least 12 months. Researchers compared their rates of cardiovascular disease with those of similar patients who did not take the supplement.
The data covered five years. Among long-term melatonin users, about 4.6% developed heart failure, compared with 2.7% of non-users. That difference amounts to a nearly 90% higher risk. The study also found that 19% of melatonin users were hospitalized for heart failure over the five-year period, versus 6.6% of non-users. In addition, 7.8% of those taking melatonin died from any cause during the study, while 4.3% of non-users died.
“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 Dr. Ekenedilichukwu Nnadi, the lead author of the study, in a statement. The researchers stressed that the findings show an association, not proof of cause and effect. Still, the consistency of the results raises questions about the safety of routine, long-term melatonin use.
The study has important limits. Chronic insomnia on its own is 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 the supplement use could be a marker of poor sleep health rather than a direct cause of heart disease. Also, the study identified “melatonin users” from prescription records. In many countries melatonin is a prescription drug, but in the United States it is sold over the counter. That means some over-the-counter users may have been wrongly counted as non-users, making it harder to measure the true difference between the groups.
Experts have long warned about unknown safety effects of melatonin, and this study adds to those concerns. Short-term, appropriately dosed melatonin may still help with occasional jet lag, but researchers say it is not meant for nightly long-term use. For people with ongoing sleep problems, other approaches may be safer.
Improving sleep hygiene is a first step. This includes avoiding alcohol late at night, keeping the bedroom dark and cool, and reducing screen time before bed. For those who want a supplement, magnesium is a common alternative. About 43% of Americans do not get enough magnesium from food alone. Low levels have been linked to stress, muscle tension, restless sleep, and mood changes. Taking magnesium before bed can help calm the nervous system by activating receptors for GABA, a neurotransmitter that quiets overactive brain activity. This may help people fall asleep and stay asleep through the night.
The study is preliminary, but it suggests that long-term nightly 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.
