Melatonin and Heart Failure Risk: What You Need to Realize

Millions rely on melatonin to improve sleep, but a growing body of research suggests long-term use may not be as benign as once thought. A recent study has raised concerns about a potential link between prolonged melatonin supplementation and an increased risk of heart failure. Here’s what the latest findings reveal and what you should consider if you regularly take melatonin.

The Study: A Warning Signal

A preliminary study presented in November 2025 at the American Heart Association (AHA) conference analyzed the medical records of 130,828 adults diagnosed with chronic insomnia. Researchers found that individuals taking melatonin for a year or more had a higher likelihood of developing heart failure. This finding is particularly relevant given the widespread use of melatonin, with approximately 1.4 million boxes of melatonin-based food supplements sold annually in France alone, according to the Order of Pharmacists.

What the Study Shows (and Doesn’t Prove)

The research, led by Dr. Ekenedilichukwu Nnadi from SUNY Downstate Hospital in Brooklyn, Modern York, compared two groups of insomniacs over five years. One group had been taking melatonin for at least twelve months, while the other did not. The groups were carefully matched based on 40 criteria, including age, sex, cardiovascular history, blood pressure, and current medications.

Here’s a breakdown of the key findings:

• Heart Failure over 5 years: 2.7% in the non-melatonin group vs. 4.6% in the melatonin group (+89% increase)
• Hospitalization for Heart Failure: 6.6% in the non-melatonin group vs. 19% in the melatonin group (a 3.5-fold increase)
• All-cause mortality: 4.3% in the non-melatonin group vs. 7.8% in the melatonin group (an 80% increase)

It’s crucial to understand that this study demonstrates a statistical association, not a proven cause-and-effect relationship. The results have not yet been published in a peer-reviewed scientific journal, and further research is needed to confirm these findings.

Who is Most Exposed to This Potential Risk?

Seniors are particularly vulnerable, as natural melatonin production tends to decline with age, leading many to seek supplementation. However, many take melatonin nightly for months or even years without medical supervision. This prolonged use is what the study associates with an increased risk.

Real Effectiveness, But More Modest Than We Believe

According to a 2024 analysis by Inserm, melatonin supplements can modestly reduce the time it takes to fall asleep, particularly in individuals over 55. However, studies show limited effects on nighttime awakenings or overall sleep quality.

What You Can Do Now

The French health authority, ANSES, recommended in 2018 limiting melatonin intake to occasional use and consulting a doctor to avoid prolonged self-medication. This American study doesn’t negate the occasional use of melatonin, but it highlights that even “natural” supplements aren’t necessarily risk-free when taken long-term, especially for those with cardiovascular risk factors.

Here’s a quick guide:

• Short-Term Use: Effectiveness on falling asleep is modest but recognized. No significant cardiac risk identified to date.
• Prolonged Use (≥1 year): Limited effects on nighttime awakenings. An 89% increased risk of heart failure was observed in the AHA 2025 study.

The Trap of “Natural Therefore Without Danger”

This study underscores a common misconception: the belief that products sold without a prescription and labeled as “natural” are inherently safe. Researchers acknowledge limitations, including the fact that chronic insomnia itself is a cardiovascular risk factor, and that other factors like depression, anxiety, or concurrent medications could contribute to the observed results. However, the signal is concerning enough to warrant increased caution.

Key Takeaways

• An American study of 130,000 insomniacs associates prolonged melatonin use (≥1 year) with an increased risk of heart failure (+89%), though a causal link hasn’t been established.
• Hospitalizations for heart failure were 3.5 times more frequent among long-term melatonin users.
• The effectiveness of over-the-counter melatonin supplements remains modest, particularly for improving nighttime awakenings.
• ANSES recommends limiting melatonin intake to occasional use and consulting a doctor.
• If you take melatonin regularly, discuss it with your healthcare provider. Cognitive and behavioral therapy (CBT-I) remains the gold standard for chronic insomnia.