Many people turn to melatonin to help calm restless nights. Most also believe that his natural sleep helper carries little downside. A preliminary large-scale study presented at the Scientific Sessions 2025 of the American Heart Association, however, suggests that long-term use might be more complicated. The research team uncovered a link between extended melatonin supplementation and an increased risk of heart problems.
Researchers Sound Caution as New Data Challenges the Safety of Melatonin Supplements
A sweeping analysis tracking adults with insomnia suggests that the benefits of melatonin may come with overlooked long term costs.
The researchers used the global electronic health record database TriNetX to examine the health records of more than 130000 adults with insomnia. They compared those who used melatonin for at least 12 months with those who avoided it. Participants with a prior diagnosis of heart failure or use of other sleep medications were excluded.
Nevertheless, analysis showed that among adults with insomnia, the subgroup with documented melatonin use of at least 12 months had about a 4.6 percent increase in new diagnosis of heart failure over 5 years. Non-users of melatonin only had 2.7 percent. Note that this is about a 90 percent relative increase when compared to melatonin users.
The team also found troubling patterns in hospital data. Individuals who relied on melatonin long-term were about 3.5 times more likely to be hospitalized for heart failure than comparable adults who avoided the supplement. Death from any cause was also higher within the melatonin group than in non-users or 7.8 percent compared to 4.3 percent.
It is worth noting that the findings did not prove melatonin directly damages the heart. The study was observational. This means that only tracked associations, rather than causes, are considered. The referenced data lacked details about actual supplement doses, lifestyle habits, underlying health issues, and the specific reasons people relied on melatonin.
Experts think chronic insomnia itself could help explain the elevated risks. Individuals who take melatonin long-term may already face higher stress levels, poorer sleep quality, or undiagnosed conditions like sleep apnea. Those invisible factors could influence the heart-related outcomes seen in the data and complicate the overall interpretation.
Another important caveat is that neither the study nor its data source indicates how much melatonin was used by the participants. The biological mechanism by which melatonin might increase the risk of heart failure was also not established. No definitive guidance to stop melatonin use was given for short-term and suitable medical use.
The study still provides a compelling observational finding that long-term melatonin use in people with insomnia is linked with substantially higher rates of new-onset heart failure, hospitalization for heart failure, and death. The findings must be interpreted with caution, given the limitations of observational data and the possibility of confounding.
Melatonin is a hormone produced in the pineal gland. Its main function is to regulate the circadian rhythm or sleep-wake cycle. Synthetic forms are widely used as sleep aids to help with issues like insomnia and time zone syndrome or jet lag. Melatonin supplements are available over the counter in many countries. Most assume it is benign.
FURTHER READING AND REFERENCE
- American Heart Association. 3 November 2025. “Long-term Use of Melatonin Supplements to Support Sleep May Have Negative Health Effects.” American Heart Association Scientific Sessions 2025. Available online