A team of researchers is sounding the alarm on the long-term use of melatonin.

They say melatonin may be linked to a higher risk of heart failure.

Researchers looked at tens of thousands of adults who took melatonin for a year or longer.

They found the patients had a 90% higher risk of heart failure over the next five years.

The study notes that the research cannot provide a direct cause and effect between melatonin use and heart failure.

The research hasn’t yet been peer-reviewed or published in a journal but will be presented at the American Heart Association’s Scientific Sessions 2025 meeting taking place Nov. 7-10.

“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 factors,” Dr. Ekenedilichukwu Nnadi, lead research author and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, said in a news release.

Experts agree more research is needed before declaring melatonin a risk.