Melatonin Linked to Heart Failure Risk in New Study, Experts Urge Caution

Melatonin supplements, which have surged in popularity as an over-the-counter sleep aid, may pose significant cardiovascular risks according to alarming new research presented by the American Heart Association (AHA).

The observational study examined five years of health records from over 130,000 adults with insomnia, with researchers discovering that long-term melatonin users faced a 90% higher risk of developing heart failure compared to non-users. The findings have prompted medical experts to question the widespread assumption that melatonin supplements are entirely harmless.

“Melatonin supplements are widely thought of as a safe and natural option to support better sleep, so it was striking to see such consistent and significant increases in serious health outcomes, even after balancing for many other risk factors,” said Ekenedilichukwu Nnadi, M.D., the study’s lead author and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn.

The research specifically evaluated participants who filled at least two melatonin prescriptions spaced at least 90 days apart. These individuals showed an 82% increased risk of developing heart failure compared to those who avoided the supplement. More concerning still, a secondary analysis revealed that melatonin users were nearly 3.5 times more likely to require hospitalization for heart failure and twice as likely to die.

This represents a significant public health concern, as heart failure currently affects approximately 6.7 million adults in the United States. The condition occurs when the heart cannot pump sufficient blood to meet the body’s needs, causing organs to receive inadequate oxygen and nutrients.

Melatonin, a hormone naturally produced by the pineal gland in the brain, helps regulate sleep-wake cycles by increasing during darkness and decreasing with exposure to light. While available over the counter in the U.S., melatonin is prescription-only in many other countries, reflecting varying regulatory approaches to its use.

Sleep expert Wendy Troxel, Ph.D., senior scientist at the RAND Corporation, described the research as “an important wake-up call” for both consumers and healthcare providers. She highlighted the misconception that natural substances are automatically safe and effective.

“In the U.S., melatonin is widely promoted and easily purchased over the counter,” Troxel explained. “Many people assume that just because it’s natural, it must be safe and effective, but that’s not necessarily the case.”

Troxel pointed to problematic issues with melatonin supplements in the American market, including dramatic variations between labeled and actual doses. She noted that commonly available 5mg and 10mg supplements contain “far greater” amounts than what the human body naturally produces.

“It’s also important to note that melatonin is not actually a sleep aid in the traditional sense,” Troxel added. “Rather, it’s a chronobiotic, meaning it helps signal to your body when it’s time for sleep, but doesn’t necessarily put you to sleep.”

The supplement’s effectiveness for chronic insomnia has been questioned in previous research, with studies showing limited evidence of its efficacy as a nightly sleep aid for most insomnia sufferers.

Beyond cardiovascular concerns, Troxel highlighted existing data showing increased emergency room visits among children who accidentally overdosed on melatonin supplements, particularly those packaged as appealing gummies.

The study did acknowledge several limitations, including lack of information on insomnia severity and presence of other psychiatric disorders. Dr. Nnadi noted that factors like depression, anxiety, or use of other sleep medications might influence both melatonin use and heart disease risk.

“While the association we found raises safety concerns about the widely used supplement, our study cannot prove a direct cause-and-effect relationship,” he cautioned. “This means more research is needed to test melatonin’s safety for the heart.”

The Council for Responsible Nutrition (CRN), responding to the findings, urged “caution and context” in interpreting the results. The organization emphasized that the research represents preliminary data that cannot establish causation, and noted that chronic insomnia itself may contribute to heart health outcomes.

“Therefore, these findings are unlikely to apply to healthy adults who use melatonin dietary supplements occasionally for sleep support,” the CRN stated.

In light of growing concerns, the CRN implemented melatonin labeling guidelines in 2024 that recommend upper dosage limits and include advisory statements like “For occasional and/or intermittent use only” and “Consult a healthcare professional if you are experiencing long-term sleep difficulties.”

Instead of relying on supplements, Troxel recommends that those suffering from sleep difficulties seek treatments with “proven long-term benefits,” particularly cognitive behavioral therapy for insomnia, which she says “consistently yields better and more lasting results” than medication.

Health experts universally advise consumers to consult with healthcare providers before adding melatonin to their sleep regimen.