A new study has raised concerns about the long-term safety of melatonin supplements, suggesting a potential link to a higher risk of heart failure. However, experts caution that the findings are still preliminary and do not prove that melatonin directly causes heart problems.
Researchers reviewed electronic health records and found that adults with chronic insomnia who used melatonin for more than a year had a 90% higher risk of developing heart failure over the next five years. They were also three times more likely to be hospitalized for heart failure and twice as likely to die from any cause, compared to similar individuals who did not take melatonin.
The study will be presented at the American Heart Association’s Scientific Sessions 2025, and has not yet undergone peer review.
Dr. Ekenedilichukwu Nnadi, lead author and internal medicine chief resident at SUNY Downstate/Kings County, said the results were “striking,” given melatonin’s reputation as a safe, natural sleep aid. Yet, he emphasized that the research cannot prove cause and effect, and more investigation is needed to understand the relationship between melatonin and heart health.
What Is Melatonin and Why Do People Take It?
Melatonin is a hormone produced by the pineal gland that regulates sleep by responding to darkness. The supplements used by millions are either synthetic or extracted from animal sources.
In the U.S., melatonin is sold as a dietary supplement, meaning the FDA does not regulate it with the same rigor as pharmaceuticals. Studies have shown that some products contain far higher doses than advertised, and may include undisclosed additives.
Limitations of the Study
The research included over 130,000 adults from the TriNetX Global Research Network. But several limitations were noted:
- Melatonin is available without a prescription in many countries, meaning some users may not appear in medical records.
- The severity of insomnia and the presence of mental health conditions were not accounted for—both factors may independently affect heart health.
- Researchers had no information on dosage, which is a key factor, as many supplements contain high or inconsistent amounts.
Experts also point out that previous studies have suggested melatonin may benefit heart failure patients, highlighting the need for clearer evidence.
Melatonin: Benefits, Risks, and MisuseWhile known for improving sleep onset, melatonin has potential side effects such as dizziness, headaches, nausea, stomach upset, low blood pressure, irritability, or confusion.
Experts recommend improving sleep hygiene first, such as:
- Limiting screen time before bed
- Reducing nighttime light exposure
- Avoiding late-night food and alcohol
- Keeping the bedroom dark, quiet, and cool
If supplements are still needed, health professionals advise choosing pharmaceutical-grade melatonin verified by the USP Dietary Supplement Verification Program for purity and accuracy.
Should You Stop Taking Melatonin?
Doctors say not yet. The new findings highlight the need for more research but do not warrant panic. Melatonin should not be used long-term without medical guidance, especially by people with existing heart conditions.
Before starting—or stopping—melatonin, experts recommend consulting a healthcare provider to determine the safest approach to managing insomnia.