A new study presented at the American Heart Association’s scientific sessions has linked melatonin, one of the most widely used over-the-counter sleep supplements in the United States, to an increased risk of heart failure. The research, which has not yet undergone peer review, analyzed electronic health records and found a statistical association between melatonin use and heart failure diagnoses. But experts are urging caution, noting that the study’s design cannot prove the supplement causes cardiac problems and that several significant gaps in the data make the findings far from definitive.
What the AHA Abstract Found
The study, presented as an abstract at the AHA conference, used an observational design to examine the relationship between melatonin prescriptions recorded in electronic health records and subsequent heart failure outcomes. Observational research of this kind can identify correlations but cannot establish that one variable directly causes another. That distinction matters here because people who take melatonin often do so for chronic insomnia or other sleep disorders, conditions that carry their own cardiovascular risk. Researchers tracked patients over time and compared heart failure diagnoses between those with documented melatonin prescriptions and those without, looking for patterns that might suggest a link.
The research also has a practical blind spot: it relied on prescription records captured in electronic health systems, meaning it likely missed a large share of actual melatonin consumption. Because melatonin is sold over the counter without a prescription, many users would not appear in the dataset at all. The study is also missing information on dosing, duration of use, and the severity of the sleep problems that prompted people to take the supplement in the first place, according to reporting from the Associated Press. Those omissions make it difficult to draw firm conclusions about whether melatonin itself, or the conditions behind its use, drives the observed association. Without granular detail on how much melatonin people took, how often they used it, and what other medications or health issues they had, the numbers can suggest a signal but cannot clarify what is actually causing it.
Why Experts Are Skeptical of the Results
Several independent experts have cautioned against reading too much into the findings. The study has not been peer-reviewed, which means it has not yet been evaluated by outside scientists for methodological rigor or accuracy. Conference abstracts, by their nature, present preliminary results and often lack the full statistical adjustments that a published journal article would include. There is broader medical skepticism about drawing clinical conclusions from conference-only findings, and this case is no exception. As health reporter Caroline Hopkins Legaspi noted in a news analysis, the research highlights uncertainties rather than delivering clear guidance for patients.
The most significant concern is confounding. People who seek out melatonin tend to have trouble sleeping, and chronic insomnia is independently linked to higher rates of hypertension, obesity, diabetes, and heart disease. If the study did not fully account for insomnia severity and these overlapping health conditions, the apparent link between melatonin and heart failure could be an artifact of the underlying sleep disorder rather than evidence of harm from the supplement. Experts also point out that people with multiple medical problems are more likely to see clinicians regularly and to have both prescriptions and diagnoses recorded in their charts, which can exaggerate associations in electronic record analyses. Without randomized controlled trials that track both sleep metrics and cardiac biomarkers over time, separating the effect of melatonin from the effect of the sleep problems it is meant to treat remains an open question.
The Regulatory Gap for Supplements
The melatonin study also highlights a structural problem in how the United States regulates dietary supplements. Unlike prescription drugs, supplements do not undergo premarket approval before reaching store shelves, according to the federal fact sheet for supplement consumers. Manufacturers are responsible for ensuring their products are safe, but the food and drug agency plays a largely reactive role. The agency monitors products through post-market surveillance and can act when safety problems emerge, but it does not evaluate efficacy or safety before a supplement goes on sale, and it generally cannot require companies to run large, long-term clinical trials.
This regulatory framework means that consumers are often left to make decisions about supplements based on incomplete evidence. The agency has taken enforcement action against companies selling supplements with illegal claims about treating cardiovascular disease, but those cases typically involve marketing violations rather than safety signals from robust clinical data. When adverse events do occur, consumers and clinicians can file reports through systems such as MedWatch, which feed into post-market safety monitoring. However, voluntary reporting captures only a fraction of real-world problems, leaving regulators with an incomplete picture of supplement safety at the population level. In the case of melatonin, that gap is especially concerning because the supplement is widely used by children and older adults, two groups that may be more vulnerable to both sleep disruption and cardiovascular disease.
Supplements and Heart Health: A Pattern of Uncertainty
The melatonin findings arrive alongside a broader pattern of research questioning whether popular supplements carry hidden cardiovascular risks. A study published in a medical journal examined the effects of regular fish oil supplement use on the clinical course of cardiovascular disease, adding another data point to the debate over whether products marketed for general wellness might have unintended cardiac consequences. Like the melatonin abstract, that research relied on observational data, underscoring how much of what is known about supplements and heart health comes from correlations rather than randomized trials. The recurring theme is that seemingly benign supplements can have complex effects when taken by people with multiple risk factors or existing disease.
The tension is especially sharp for melatonin because of its sheer popularity. Millions of Americans use it regularly, often without consulting a physician, and many assume that its over-the-counter status signals that it has been thoroughly vetted. In reality, supplement oversight sits within a broader public health system that includes the health department, research agencies such as the national institutes, and coordinating offices like the Division of Program Coordination that help set research priorities. Those institutions have funded extensive work on sleep, circadian biology, and cardiovascular disease, but targeted, long-term trials focused on melatonin supplements remain limited. As a result, clinicians must balance the known benefits of better sleep against the unknowns of chronic supplement use when advising patients.
What Patients and Clinicians Can Do Now
For people who rely on melatonin, the new heart failure signal is a prompt to reassess, not necessarily to panic. Experts quoted in news coverage emphasize that stopping melatonin abruptly is not required based on a single, non-peer-reviewed abstract. Instead, they recommend that patients discuss their sleep issues and overall cardiovascular risk with a clinician, especially if they have existing heart disease, high blood pressure, or diabetes. A careful review can help determine whether insomnia might be better addressed through behavioral strategies, prescription sleep medications with more established safety profiles, or adjustments in timing and dose of melatonin rather than long-term, unsupervised use.
Clinicians, for their part, may want to ask more routinely about supplement use when evaluating patients with sleep complaints or unexplained cardiovascular symptoms. Because over-the-counter products often go unmentioned in medical visits, incorporating specific questions about melatonin and other common supplements can clarify the full picture of a patient’s regimen. Until more definitive data are available, many experts suggest using the lowest effective dose for the shortest necessary duration, avoiding high-dose formulations, and being especially cautious in older adults and those with multiple cardiac risk factors. The emerging research does not prove that melatonin causes heart failure, but it does reinforce a broader message: even familiar supplements are active biologic agents and should be treated with the same respect and scrutiny as other medications.
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*This article was researched with the help of AI, with human editors creating the final content.
