Is Long-Term Melatonin Use Linked to Heart Failure? What the New Study Really Found
If you have trouble sleeping, melatonin can seem like an easy answer. It is widely available, often marketed as a natural sleep aid, and many people assume that something produced naturally by the body must be harmless.
But new research is raising questions about what may happen when melatonin supplements are used regularly for a long time.
A preliminary study presented at the American Heart Association’s Scientific Sessions 2025 found an association between long-term melatonin use and a higher risk of heart failure, hospitalization for heart failure and death from any cause among adults with chronic insomnia.
The findings sound alarming. However, there is an important caveat: the research is an observational study presented as a scientific meeting abstract, meaning it has not yet been peer-reviewed as a full research paper and cannot prove that melatonin causes heart problems.
What Did the Study Find?
Researchers reviewed five years of electronic health records involving 130,828 adults with insomnia. People whose records showed melatonin use for at least 12 months were compared with similar people with insomnia who did not have melatonin recorded in their medical records.
The researchers found that long-term melatonin users had about a 90% higher chance of developing heart failure during the five-year period. Heart failure occurred in approximately 4.6% of the melatonin group compared with 2.7% of the comparison group.
The study also reported higher rates of heart-failure hospitalization and death from any cause among people in the long-term melatonin group.
Those numbers deserve attention, but they should not be interpreted as meaning that taking melatonin gives a person a 90% chance of developing heart failure.
The researchers were reporting a relative difference between groups, not proof that melatonin itself caused the additional cases.
Does Melatonin Actually Cause Heart Failure?
That is the biggest unanswered question.
The study was observational, meaning researchers looked at existing health records rather than randomly assigning people to take melatonin or a placebo. This type of research can identify an association, but it cannot establish cause and effect.
There may be important differences between people who regularly take melatonin and those who do not.
For example, people taking melatonin for a year or longer may have more severe or persistent insomnia. They may also have other health conditions, mental-health concerns or sleep disorders that affect cardiovascular health.
The researchers themselves acknowledged that factors such as insomnia severity, anxiety, depression and other sleep-related treatments could have influenced the results.
There is another major limitation. Because melatonin is available without a prescription in the United States, electronic health records may not capture every person who actually takes it. That makes it difficult to know exactly how much melatonin participants used or how consistently they took it.
Why the “Natural” Label Can Be Misleading
Melatonin is a hormone naturally produced by the body. It helps regulate the sleep-wake cycle, with levels generally increasing in darkness.
But a supplement is still a supplement. Products can differ in strength and formulation, and long-term safety data are not as extensive as many consumers might assume.
The American Heart Association noted that long-term cardiovascular safety data for melatonin remain limited. The organization also emphasized that the new findings need further research before firm conclusions can be made.
That distinction is important. “Natural” describes where a substance comes from; it does not automatically mean that taking additional amounts every night for years is risk-free.
What About People Who Occasionally Take Melatonin?
The new research does not show that occasional melatonin use causes heart failure.
The study specifically examined people with insomnia whose records indicated long-term use, generally defined as at least one year. It therefore cannot tell us that taking melatonin occasionally for travel, a temporary change in schedule or another short-term situation will cause cardiovascular problems.
If you are taking melatonin regularly, however, the study is a reasonable reminder to look at why you need it rather than simply continuing indefinitely.
Chronic difficulty sleeping can sometimes be related to an underlying sleep disorder or another health issue that deserves attention.
Better Ways to Manage Chronic Insomnia
For people with persistent insomnia, simply taking a sleep supplement may not address the underlying problem.
Sleep specialists commonly use Cognitive Behavioral Therapy for Insomnia (CBT-I), a structured behavioral treatment designed specifically for chronic insomnia. Earlier American Academy of Sleep Medicine guidance has also noted limited evidence for long-term use of over-the-counter insomnia treatments and recommended behavioral approaches when appropriate.
Simple sleep habits can also help, although they are not a substitute for medical care when insomnia continues.
Keeping a consistent sleep schedule, creating a comfortable bedroom environment and avoiding stimulating activities close to bedtime can support healthier sleep patterns.
The Bottom Line
The new research adds an important question to the conversation about long term melatonin heart failure risk, but it does not provide a final answer.
Researchers found that adults with chronic insomnia who had long-term melatonin use documented in their medical records experienced higher rates of heart failure, heart-failure hospitalization and death during five years of follow-up. However, the study was observational, preliminary and not designed to prove that melatonin caused those outcomes.
For now, the sensible takeaway is not to panic about an occasional melatonin dose. Instead, people who depend on melatonin night after night for months or years should discuss their sleep problems with a healthcare professional.
The bigger health question may not simply be whether melatonin is safe. It may be why someone needs a sleep aid for so long in the first place—and whether an underlying sleep or health problem is going untreated.
Photo by Marek Studzinski on Unsplash
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