Popular Supplement Linked to Heart Disease in Millions, New Study Warns

New research has raised concerns about the long-term use of melatonin supplements, linking them to a significantly increased risk of heart failure in adults with chronic insomnia. The findings come from an observational study presented at the American Heart Association’s Scientific Sessions 2025, which analyzed five years of health records from over 130,000 adults with insomnia.

According to the study, individuals who used melatonin supplements for at least one year had a 90% higher chance of developing heart failure compared to those who did not take the supplement. A secondary analysis showed that participants who filled at least two melatonin prescriptions at least 90 days apart had an 82% increased risk of heart failure.

The research also found that long-term melatonin users were nearly 3.5 times more likely to be hospitalized for heart failure and twice as likely to die from any cause over the five-year period. These associations remained after excluding participants who were prescribed other sleep medications or who already had confirmed heart failure at the start of the study.

Melatonin is a hormone naturally produced by the body that helps regulate the sleep-wake cycle, with levels rising in darkness and decreasing with light exposure. Synthetic versions of the hormone are widely available over the counter and commonly used to treat insomnia and jet lag. The study’s lead researchers emphasized that while the findings show a strong association, they do not prove causation, and further research is needed to understand the potential cardiovascular effects of long-term melatonin use.

The study was described as preliminary, as it was presented as a research abstract at the American Heart Association meeting and has not yet been published in a peer-reviewed journal. Experts caution that observational studies like this one can identify patterns but cannot establish cause-and-effect relationships, and other factors may influence the observed risks.

Health professionals advise individuals currently using melatonin supplements to consult with their healthcare providers about the potential risks and benefits, particularly if they have underlying health conditions or are using the supplement long-term. They also recommend discussing alternative strategies for managing insomnia, such as cognitive behavioral therapy for insomnia or lifestyle changes, when appropriate.