New study links long-term melatonin use to higher rates of heart failure – raising questions for clinicians recommending sleep support.
Melatonin may be the supplement that launched a thousand bedside tables; in the age of blue light, jet lag and stress-induced insomnia, the “natural sleep hormone” has become a fixture of nighttime routines. Yet new research suggests that long-term use could have unintended consequences for heart health – particularly for those already at risk.
A study presented at the American Heart Association’s Scientific Sessions 2025 examined data from more than 170,000 adults and found that people who regularly took melatonin supplements for over a year were significantly more likely to experience heart failure [1]. While melatonin has long been considered a relatively safe over-the-counter option, these findings suggest that the compound’s effects on cardiovascular function may be more complex than previously thought.
Sleep support or silent strain
Melatonin is a hormone produced by the pineal gland that helps regulate circadian rhythm; supplementation is intended to mimic this natural pattern and ease the transition to sleep. However, when taken chronically – especially in higher doses than the body produces naturally – it may disrupt other physiological systems, including blood pressure regulation and cardiac metabolism.
The new study’s lead author, Dr Wendy Troxel of the RAND Corporation, noted that while melatonin is often perceived as benign, “there’s very little long-term data on its safety or efficacy.” The association found between habitual use and heart failure doesn’t necessarily prove causation, but it raises concerns about how prolonged supplementation might influence cardiovascular pathways over time.
Animal studies have hinted at both protective and detrimental cardiac effects, depending on dose, timing and metabolic state. For humans, the story seems similarly nuanced: short-term melatonin use can improve sleep quality and reduce oxidative stress, yet chronic exposure may interfere with blood vessel tone or hormone signalling – subtle effects that, accumulated over years, could have consequences for heart health.
Not so harmless after all
Dr Ernst von Schwarz, a Los Angeles-based cardiologist and UCLA professor, likens the situation to the once-widespread use of aspirin as a daily preventive measure. “While melatonin is generally safe to take once in a while, individuals should not take it every day,” he says, cautioning that habitual use could irritate organs much as aspirin can affect the stomach, intestines and kidneys.
Von Schwarz, who also directs a regenerative medicine clinic in Beverly Hills, argues that clinicians must distinguish between therapeutic use and habitual dependence. For patients struggling with insomnia or circadian disruption, melatonin can provide a short-term bridge – but it should not become a nightly crutch.
A wake-up call for clinics
For longevity and integrative health clinics, where sleep quality is rightly seen as foundational to healthy aging, this research invites reflection. Many clinics include melatonin among their sleep-support protocols, often paired with stress management, light therapy or magnesium supplementation. Yet if the hormone’s long-term effects on cardiac function prove clinically significant, practitioners may need to rethink dosage, duration and patient screening.
Chronic insomnia is not only distressing but biologically corrosive – poor sleep drives inflammation, insulin resistance and cognitive decline. However, the solution may lie less in supplement aisles and more in personalized sleep strategies: addressing underlying hormone imbalance, circadian misalignment and lifestyle contributors.
Clinicians might consider functional testing to understand whether disrupted melatonin production reflects adrenal fatigue, exposure to artificial light, or other metabolic disturbances. Where supplementation remains necessary, short courses at physiological doses (typically 0.3–1 mg) may support rhythm restoration without risking long-term desensitisation.
The fine line between aid and interference
Sleep is deeply biological, but also exquisitely sensitive to interference. The body’s internal clock depends on the interplay between light, temperature, hormones and neural cues – a system easily thrown off by irregular habits or poorly timed supplementation. Artificially sustaining high melatonin levels can, paradoxically, blunt the body’s own production and distort the subtle dance between night and day that governs everything from digestion to cardiovascular function.
For clinicians, this is a call to weigh benefit against burden. Just as hormone replacement therapy is personalized and monitored, so too should exogenous melatonin be used with clinical oversight rather than consumer enthusiasm. The boundary between biohack and biological overreach remains slender.
Help is at hand
For anyone struggling with sleep disruption – or simply curious about their hormonal rhythms – expert help is available. Our Longevity Clinics Directory lists clinics that combine medical oversight with modern diagnostic tools; places where sleep panels, circadian assessments and metabolic profiling are routine, not radical. Rather than trawling the internet for advice of mixed reliability, readers can find trusted specialists who will listen, test and tailor a plan to their needs.
A rhythm worth protecting
As ever, the goal is balance. Sleep is one of biology’s most elegant feedback loops – interfere too much and the system falters. Melatonin remains a useful clinical tool when deployed judiciously; the key, as with so much in longevity medicine, is to support the body’s own rhythm, not replace it.
