Long-Term Melatonin Use Linked To Nearly Double Heart Failure Risk, Study Finds

Authored by Cara Michelle Miller via The Epoch Times (emphasis ours),

Melatonin, a natural hormone, is often labeled a heart-healthy sleep aid. However, an extensive new study suggests that regular users face a higher risk of developing heart failure, hospitalization, and even death over time.

Adults with chronic insomnia who used melatonin for a year or longer faced a 90 percent higher risk of developing heart failure within five years compared to non-users.

The preliminary analysis, presented Monday at the American Heart Association’s Scientific Sessions 2025, tracked more than 130,000 adults diagnosed with insomnia. Among those who took melatonin for more than a year, 4.6 percent developed heart failure, compared with 2.7 percent of nonusers.

Melatonin users were also more than three times as likely to be hospitalized for heart failure and had almost double the risk of dying from any cause. Still, the two groups differed only modestly in absolute terms—7.8 percent of long-term melatonin users died during the study period versus 4.3 percent in those not taking melatonin—a gap of about 3.5 percentage points.

“The takeaway isn’t that melatonin is ‘bad’ or that everyone should stop taking it,” Dr. Ekenedilichukwu Nnadi, chief resident in internal medicine at SUNY Downstate Health Sciences University, who led the research, told The Epoch Times in an email. “It’s that we shouldn’t assume something is risk-free just because it’s natural or sold over the counter.”

Melatonin, a hormone the body naturally produces at night, is often regarded as a safe, easy fix for insomnia and is frequently taken nightly by people struggling to sleep. Its use has more than doubled over the past decade, with about 12 percent of Americans diagnosed with chronic insomnia and millions more struggling to sleep most nights.

What the Study Found

Researchers used data from more than 130,000 adults diagnosed with insomnia. Roughly half had been prescribed melatonin or reported self-use; the rest had no melatonin use. None had heart failure or used prescription sleep aids at the start of the study.

The results held even when researchers required multiple prescriptions to define “chronic use,” reinforcing a link to long-term, versus occasional, melatonin use.

“This doesn’t prove that melatonin directly causes heart failure,” said Nnadi, noting that the study was observational. People who take melatonin every night may simply have more severe insomnia, which itself could raise heart risks.

Still, the study’s size and careful matching make the findings notable—and raise important questions about supplement safety, he said.

“It shows that people with chronic insomnia who took melatonin long-term were more likely to experience these outcomes. It’s an unexpected and important signal that needs to be studied further.”

What the Study Can’t Tell Us

The research could only track prescribed melatonin, since some over-the-counter use isn’t recorded in medical records. That means some people counted as “nonusers” may have taken melatonin without telling their doctors.

“That would actually bias the results toward no difference. In other words, it would make melatonin look safer than it might be,” said Nnadi. “So the fact that we still saw a strong, consistent association suggests the signal is real.”

“Of course, this limitation is exactly why we need randomized, prospective trials to confirm whether melatonin itself is contributing to these risks.”

Unlike prescription drugs, melatonin supplements are not strictly regulated.

The actual amount of melatonin can vary widely from one brand to another. A study found that the amount of melatonin you get can vary significantly from what’s on the label—ranging from -83 percent to +478 percent—suggesting that some products may supply far higher levels than the body is designed to handle.

Most people in the United States buy melatonin over the counter, without any prescription, and may take it for months or years. In the UK, Australia, and the European Union, melatonin is available only by prescription for short-term treatment of insomnia.

Mixed Evidence on Heart Effects

Melatonin also acts as an antioxidant and has been associated with improved heart benefits for people with existing heart issues—improving heart function and reducing stress on the heart muscles. However, these studies were small, short-term trials on animals or carefully selected patients using pure, prescription-strength melatonin.

“Our study is different,” said Nnadi. “We looked at real-world use: supplements taken nightly for years, in diverse populations with varying doses and product quality in patients that specifically have chronic insomnia. That’s a very different scenario.”

Melatonin helps regulate the body’s sleep-wake cycle, peaking at night to signal the brain that it’s time to rest. For people with insomnia, taking melatonin before bed can help promote sleepiness and support a more restful night. It can also modestly influence blood pressure and heart rate as the body transitions to rest.

Although the study didn’t identify a mechanism, possible effects could involve heart rhythm, blood pressure, or metabolism—effects that are not fully understood—especially with supplements taken over many months or years.

Insomnia itself, meanwhile, has been linked in previous research to increased inflammation, higher nighttime blood pressure, and changes in stress hormones such as cortisol—all of which can strain the heart over time and raise the risk of heart failure.

Expert Recommendations

Marie-Pierre St-Onge, a sleep researcher at Columbia University who was not involved in the study, said in her preliminary analysis that she was surprised that some patients were prescribed melatonin for more than a year.

“Melatonin, at least in the U.S., is not indicated for the treatment of insomnia,” said St-Onge, who chairs the writing group for the American Heart Association’s 2025 scientific statement, Multidimensional Sleep Health: Definitions and Implications for Cardiometabolic Health, adding that “people should be aware that it should not be taken chronically without a proper indication.”

The Council for Responsible Nutrition, a trade group for supplement manufacturers, agreed that melatonin should be used occasionally and that anyone with long-term sleep difficulties should consult a medical professional before using it.

What Should You Do?

For those struggling with consistent sleep, Dr. Muhammad A. Rishi, a sleep medicine physician at Indiana University Health, previously wrote to The Epoch Times via email that melatonin supplements should be used carefully.

Even though melatonin is a naturally occurring hormone, Rishi said that the supplements change a person’s mental or physical state, and therefore, should be treated as a drug.

Common side effects include headaches and dizziness; it can also interact with other medicines, such as anticoagulants—drugs that help prevent blood clots. Sleep doctors typically advise starting with the lowest effective dose—about 0.5 to 1 milligram—taken one to two hours before bedtime, and only for one to three months. Long-term effects remain unknown.

Persistent insomnia can signal an underlying condition, such as sleep apnea, restless legs syndrome, depression, or chronic pain. When a sleep specialist identifies the correct diagnosis, treatment options can then be explored.

“For people using melatonin occasionally or short-term, it may still be fine. But for those taking it nightly for years, especially with heart disease or risk factors, it’s worth having a conversation with your doctor,“ Nnadi said. ”We need to treat supplements with the same care and skepticism as prescription drugs.”

“Our study,” he added, “is a reminder that more isn’t always better, and that we need stronger evidence before calling any supplement ‘heart-healthy.’”