A new preliminary study is raising concerns about the long-term use of melatonin supplements among people with chronic insomnia. The research, presented in November at the American Heart Association’s Scientific Sessions 2025 in New Orleans, suggests that using melatonin for a year or more may be linked to a higher risk of heart problems.

The study hasn’t been peer-reviewed, so the findings should be viewed as early evidence, not final answers. The results highlight the need for more research into how melatonin affects long-term health.

What the study found

Researchers reviewed five years of electronic health records from 130,828 adults diagnosed with insomnia. The average age was 55.7 years, and about 61% were women. They compared people who used melatonin long-term, meaning at least 12 months recorded in their medical record, with similar adults who had insomnia but no record of melatonin use.

The main analysis found that adults with chronic insomnia who used melatonin long-term had about a 90% higher chance of developing heart failure over five years compared with adults who didn’t take melatonin (4.6% vs. 2.7%).

The study also found that people taking melatonin were nearly 3.5 times more likely to be hospitalized for heart failure than those not taking it (19.0% vs. 6.6%).

The researchers note some limitations. The database included countries where melatonin requires a prescription and places like the U.S. where it does not. Because the study relied on prescriptions and documented medication use, many people who take over-the-counter melatonin would have been counted as non-users. That means the findings may not fully reflect real-world use.

What is melatonin?

Melatonin is a hormone your body naturally produces. It helps regulate your sleep-wake cycle by signaling when the time for sleep is approaching.

Melatonin supplements are widely available in the U.S., with over-the-counter supplements available in doses from 1 to 10 milligrams. However, because melatonin is sold as a dietary supplement, it is not regulated by the FDA. That means it is possible for the content of the supplement to differ from what is listed on the product label.

A  2017 study in the Journal of Clinical Sleep Medicine found that the melatonin content of dietary supplements often varies widely from what is listed on the label. Results show that the melatonin content in more than 71% of supplements differed from the label by more than 10%, ranging from 83% less to 478% more than the label stated. Levels even varied from one batch to another within the same brand.

Melatonin can be effective for certain circadian rhythm disorders, but there is little to no evidence that it works well as a general sleep aid. Still, many people use it to self-treat insomnia.

Growing use and safety advisories

Melatonin use has increased in the last two decades across all ages, a trend supported by research showing significant growth in reported supplement use among U.S. adults from 1999 through 2018.

Following the pandemic, there was a spike in emergency calls related to suspected child melatonin overdoses. In response, the American Academy of Sleep Medicine issued a health advisory urging parents to seek medical guidance before giving melatonin to children or teens.

Experts continue to stress caution, especially because supplement content varies so widely and long-term effects remain unclear.

Understanding insomnia

Because many people take melatonin to manage insomnia, it helps to understand what insomnia is and how it is usually treated.

Chronic insomnia means having trouble sleeping at least three times per week for three months or longer. About 10% of adults experience it.

Treatment depends on the cause, but sleep specialists recommend trying healthy sleep habits first for short-term insomnia. For chronic insomnia, however, lifestyle changes often are not enough.

The American Academy of Sleep Medicine recommends cognitive behavioral therapy for insomnia, or CBT-I, as the first-line treatment for chronic insomnia in adults. CBT-I includes strategies to change unhelpful thoughts and behaviors around sleep. Medications are generally reserved for people who cannot participate in CBT-I, who still have symptoms after therapy, or who need short-term help along with CBT-I.

Key takeaways

This new study found an association between long-term melatonin use and heart risks. It did not show that melatonin causes heart failure. More research is needed before experts can say whether long-term melatonin use affects heart health.

Melatonin may seem like a simple fix for trouble sleeping, but it is not risk-free, and it may not help with insomnia in the first place. If you are struggling with chronic sleep problems, talk to a health professional or get help from the sleep team at an accredited sleep center.

Medical review by Helena Schotland, MD

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Authored by: Kate Robards