Why Your Sleeping Pill Might Strain Your Heart

You have done everything right before bed: dimmed the lights, silenced your phone, and climbed under the covers. Yet sleep refuses to arrive. So, like millions of others, you reach for that tiny tablet that promises rest: melatonin.

For decades, melatonin has been marketed as a harmless and natural way to fall asleep. But new research suggests that long-term use of the supplement may not be as innocent as once thought. Scientists now warn that chronic melatonin use could be linked to a 90 percent higher risk of heart failure in adults with insomnia. The study, presented at the 2025 American Heart Association (AHA) Scientific Sessions in New Orleans, is forcing experts and consumers alike to rethink how we approach sleep.

What the Study Revealed

The research, led by Dr. Ekenedilichukwu Nnadi of SUNY Downstate/Kings County Primary Care, analyzed electronic health records from over 130,000 adults with chronic insomnia. Roughly half of the participants had used melatonin regularly for at least a year, while the rest had not.

Over a five-year follow-up period, those who used melatonin long term were found to have a 90 percent higher chance of developing heart failure compared to non-users. Specifically, 4.6 percent of long-term users developed heart failure, compared with 2.7 percent of those who did not take melatonin. Long-term users were also 3.5 times more likely to be hospitalized for heart failure and nearly twice as likely to die from any cause during the same time frame.

To isolate melatonin’s effect, the study excluded people who already had heart failure or who were taking other sleep medications such as benzodiazepines. Even with those exclusions, the differences between groups were significant.

The researchers stressed that their study was observational and did not prove causation. Still, the association between melatonin use and cardiovascular outcomes was strong enough to raise questions about the supplement’s long-term safety.

Is Melatonin the Problem, or a Warning Sign?

The findings triggered a wave of debate among scientists and sleep specialists. While some interpret the data as evidence that long-term melatonin use could strain the heart, others suggest the opposite: that frequent melatonin use may simply signal an underlying issue.

“Insomnia can increase blood pressure, stress hormones, and inflammation,” explained Dr. Nnadi. “Those factors alone raise the risk of heart failure. So melatonin use might just be a marker of people whose bodies are already under stress.”

Dr. Nishant Shah, a preventive cardiologist at Duke University, said that while the results are compelling, they should be interpreted with caution. “It is too early to claim that melatonin itself causes harm. But this study does highlight how important it is to examine the long-term effects of sleep agents,” he said.

The researchers also acknowledged the study’s limitations. Because melatonin is sold over the counter in the United States, most purchases are not recorded in medical databases. That means many long-term users might not have been included in the study at all, making the actual scope of use much broader.

Why Doctors Are Concerned

The concern stems from melatonin’s widespread use and its reputation as a gentle, natural solution. In the United States, the supplement is available without a prescription and often used by people seeking alternatives to stronger medications. But experts warn that its popularity has outpaced the science behind its safety.

Dr. Cheng-Han Chen, a cardiologist at MemorialCare Saddleback Medical Center in California, believes that melatonin use often masks more serious problems. “If you are relying on melatonin every night, it may be a sign that your body’s internal rhythms are disrupted,” he said. “That disruption itself could affect your heart.”

During deep sleep, heart rate slows, blood pressure drops, and the cardiovascular system undergoes repair. When sleep is fragmented or delayed, those restorative processes are cut short. Over time, this can lead to chronic stress on the heart, increasing the risk of hypertension, arrhythmia, and eventually heart failure.

Dr. Chen’s advice is straightforward: “If you are taking melatonin nightly and still feel unrested, talk to your doctor. It is possible that poor sleep is not the problem, but a symptom of something else.”

The Myth of “Natural” Safety

One of the biggest misconceptions about melatonin is that because it is natural, it must be harmless. The truth is more complicated. The pineal gland produces melatonin naturally in small amounts, measured in micrograms. Yet the average supplement contains between three and ten milligrams hundreds of times more than the body typically makes.

Because melatonin is classified as a dietary supplement, the U.S. Food and Drug Administration does not regulate its purity or dosage as strictly as prescription drugs. Independent tests have found that the actual melatonin content in some products can vary by up to 400 percent from what is printed on the label.

Dr. Jamie Alan, a pharmacology professor at Michigan State University, warns that this inconsistency could be one reason for unexpected side effects. “Hormones are incredibly powerful chemicals,” she said. “When you introduce them in excess or at the wrong time, you can throw off multiple systems in the body, including cardiovascular function.”

In addition to regulating sleep, melatonin influences body temperature, immune function, and blood pressure. Excessive or poorly timed doses could disrupt these processes, placing subtle but chronic stress on the heart.

How Modern Life Fuels the Problem

The rise of melatonin mirrors a global shift in how society sleeps or fails to. Between 1999 and 2018, melatonin use among U.S. adults increased fivefold. Today, more than five million Americans report taking it regularly. The supplement’s popularity coincides with soaring rates of insomnia, anxiety, and late-night screen use.

Artificial light and digital devices emit blue wavelengths that suppress the body’s natural melatonin production, tricking the brain into staying alert long after sunset. The result is a generation out of sync with its natural circadian rhythm.

“We are asking our bodies to sleep in a world that never goes dark,” said Dr. Christopher Winter, a neurologist specializing in sleep. “Melatonin supplements can help temporarily, but they do not fix the root cause of our disconnection from natural light cycles.”

That disconnection is not merely an inconvenience. Chronic circadian misalignment has been linked to higher risks of obesity, diabetes, depression, and heart disease. Over time, the body forgets when to rest and when to recover, leaving the cardiovascular system constantly overworked.

Alternatives for Better Sleep

The good news is that there are safer, more sustainable ways to reclaim healthy sleep without long-term reliance on supplements. Sleep experts recommend adopting practices known collectively as sleep hygiene. These small, consistent habits help restore the body’s natural rhythm.

1. Maintain a consistent sleep schedule, going to bed and waking up at the same time each day.
2. Avoid blue light exposure at least one hour before bed by turning off phones, tablets, and televisions.
3. Keep the bedroom cool, dark, and quiet to create an environment that signals the body to wind down.
4. Avoid caffeine, nicotine, and alcohol close to bedtime, as they can delay or fragment sleep.
5. Consider cognitive behavioral therapy for insomnia (CBT-I), which addresses the thoughts and habits that interfere with rest.

Daytime habits matter as well. Getting natural sunlight early in the morning helps suppress melatonin when you wake, setting the stage for a smoother release of the hormone at night. Physical activity and mindful stress management, like deep breathing or meditation, can further support this natural cycle.

The Heart’s Hidden Rhythm

The American Heart Association lists sleep among its “Essential 8” factors for cardiovascular health, alongside diet, exercise, and blood sugar management. During restorative sleep, the heart slows its pace and blood pressure drops, allowing it to recover from daily strain.

When sleep is disrupted for months or years, those recovery periods vanish. A 2024 study in the journal Frontiers found that people who regularly went to bed after midnight faced a significantly higher risk of heart attack compared to those who slept earlier. The researchers concluded that both sleep duration and timing play crucial roles in maintaining cardiovascular stability.

Melatonin, as the hormone that orchestrates our internal night signal, sits at the center of this system. When we supplement it artificially, especially in excess, we risk desynchronizing the delicate rhythm between the brain and the heart. Over time, this disruption could erode the very balance that keeps the cardiovascular system strong.

A Society Out of Sync

Melatonin’s story reflects a deeper truth about modern life. Our 24-hour culture prizes productivity and stimulation over rest. The boundaries between day and night have blurred, and so we turn to chemistry to do what lifestyle once managed naturally.

But as this new research reminds us, shortcuts can carry hidden costs. Using melatonin nightly to fight off sleeplessness may offer short-term relief, but it might also mask underlying health problems such as anxiety, high blood pressure, or even early heart dysfunction.

“Melatonin is not the villain,” said Dr. Nnadi. “It is a signal, both biologically and metaphorically. When your body depends on it, something deeper may be out of rhythm.”

Rethinking Sleep, Respecting the Body

The discovery that long-term melatonin use might increase heart failure risk is not a reason to panic. Instead, it is an invitation to look closer at how we approach rest. Short-term use, especially at low doses, remains generally safe under medical guidance. The issue arises when supplements become a substitute for balance.

Our bodies evolved to sleep in sync with the earth’s light and darkness. Every sunrise suppresses melatonin, every sunset calls it back. This ancient rhythm keeps the heart, brain, and metabolism aligned. When we disrupt that balance with artificial light and stress, no supplement can fully compensate.

True sleep, as Dr. Winter explains, is not something we force but something we allow. It comes naturally when our environment and habits support it.

In the end, the lesson from this research may be less about melatonin and more about listening to what our bodies are telling us. The heart and the sleep cycle are partners in the same rhythm. When one falls out of tune, the other feels it too.

The best medicine, then, might not come in a bottle but in rediscovering the simple rituals that prepare the body for rest: dimming the lights, quieting the mind, and letting darkness do its quiet work. In a world obsessed with control and productivity, sleep remains one of the last acts of surrender and perhaps, the most vital one for the heart.