Melatonin supplements are popular. Millions of people take them to sleep better. But new research suggests that long-term melatonin use might increase the risk of heart failure.
This finding surprised many doctors and researchers. The study was presented at the American Heart Association’s Scientific Sessions 2025 in November. It looked at over 130,000 adults who struggled with insomnia.
The results showed something unexpected. People who used melatonin for more than a year had a 90% higher chance of developing heart failure within five years compared to those who didn’t use it.
But there’s more to this story. The research hasn’t been peer-reviewed yet. Other studies actually show melatonin might help heart health. So what should you believe?
What the New Study Found
Researchers analyzed medical records from almost 131,000 adults with chronic insomnia. The average age was around 56 years old. About half of them had received at least one melatonin prescription and took it for a year or longer.
The findings were striking. Adults using melatonin for more than 12 months showed a 90% increased risk of heart failure over five years. Those who filled at least two prescriptions 90 days apart had an 82% higher risk.
The news got worse. Melatonin users were 3.5 times more likely to be hospitalized for heart failure. They were also twice as likely to die from any cause during the follow-up period.
Dr. Ekenedilichukwu Nnadi led the study. He’s a chief resident in internal medicine at SUNY Downstate. He said the results were striking because melatonin supplements are widely seen as safe and natural.
Important Limitations You Should Know
This study doesn’t prove that melatonin directly causes heart failure. It only shows an association. There’s a big difference between the two.
The research is observational. This means researchers looked at existing medical data. They didn’t run a controlled experiment. Many other factors could explain the link between melatonin and heart failure.
People taking melatonin might have more severe insomnia. They might also struggle with depression or anxiety. These conditions themselves are risk factors for heart disease. The study tried to account for these factors but couldn’t eliminate them completely.
Another issue is that many Americans buy melatonin over the counter. This type of use wouldn’t show up in prescription records. So the control group (people supposedly not using melatonin) might actually include melatonin users. This would make the real difference between groups smaller than reported.
Dr. Kanika P Mody is a cardiologist at Hackensack University Medical Center. She wasn’t involved in the study. She pointed out that insomnia itself might be masking early signs of heart failure in some cases.
The Contradictory Evidence on Melatonin and Heart Failure
Here’s where things get confusing. Multiple other studies suggest melatonin might actually help people with heart problems.
A systematic review published in 2025 looked at melatonin’s effects on heart failure patients. Researchers found that melatonin improved several important measures. It helped with ejection fraction (how well the heart pumps blood). It improved functional capacity. Patients reported better quality of life.
The review concluded that melatonin could be considered as a treatment option for heart failure patients.
Other research shows melatonin has protective properties for the cardiovascular system. It works as a powerful antioxidant. This means it protects cells from damage caused by unstable molecules called free radicals.
Melatonin also reduces inflammation in the body. Chronic inflammation contributes to heart disease. Studies show melatonin can improve how blood vessels work. It helps them relax and expand properly.
Research has found melatonin might prevent the heart muscle from getting too thick. This thickening (called hypertrophy) can lead to heart failure. Melatonin also appears to protect heart tissue when blood flow is restored after a blockage.
Dr. Carlos Egea is president of the Spanish Federation of Sleep Medicine Societies. He questioned the new study’s methodology. He pointed to systematic reviews showing positive cardiovascular effects of melatonin.
So which is true? The answer isn’t clear yet. More research is needed.
How Melatonin Affects Your Heart
Understanding how melatonin works in your body helps make sense of the conflicting research.
Melatonin is a hormone your body produces naturally. The pineal gland in your brain makes it when it gets dark outside. This hormone regulates your sleep-wake cycle (circadian rhythm).
But melatonin does more than control sleep. It interacts with many systems in your body, including your heart and blood vessels.
As an antioxidant, melatonin neutralizes harmful molecules. Oxidative stress damages cells and contributes to many diseases, including heart failure. Melatonin’s antioxidant properties might protect heart cells from this damage.
Melatonin affects how your blood vessels function. Healthy blood vessels can expand and contract smoothly. This helps regulate blood pressure and ensures good blood flow. Research shows melatonin improves this function through effects on nitric oxide, a molecule that helps blood vessels relax.
The hormone also influences inflammation levels. Excessive inflammation harms the cardiovascular system over time. Melatonin appears to modulate immune responses and reduce inflammatory markers in the blood.
Some studies suggest melatonin affects heart rate and cardiac output. It might lower blood pressure in some people. These effects could be beneficial or potentially problematic depending on individual circumstances.
Safe Dosage and Usage Guidelines
If you’re currently taking melatonin, you don’t need to panic. Short-term use hasn’t been linked to the same concerns as long-term use.
Standard doses range from 1 to 3 mg for adults. The NHS in the UK recommends starting with 2 mg slow-release tablets. These are taken 30 to 60 minutes before bedtime.
Dr. Yu-Ming Ni is a cardiologist at MemorialCare Heart and Vascular Institute. He suggests capping melatonin at 1 to 3 mg nightly. Higher doses can actually backfire. You might have more trouble falling asleep if you take too much.
Timing matters too. Melatonin needs at least one to two hours before sleep to work properly. The hormone’s effect on sleepiness builds slowly.
Maximum recommended doses typically don’t exceed 5 to 10 mg. But most people should stick to lower amounts. Starting with 0.5 to 1 mg is often enough for beginners.
The NHS recommends limiting use to 13 weeks for insomnia in adults. Longer use should only happen under medical supervision. The new research on melatonin and heart failure makes this guideline seem even more important.
What Experts Are Saying
Medical professionals are taking these findings seriously but urging caution about jumping to conclusions.
Dr. Nnadi, who led the study, emphasized that the research can’t prove causation. The association they found raises safety concerns. But it doesn’t mean melatonin directly causes heart problems in everyone who takes it.
Dr. Mody called the findings noteworthy and unexpected. Previous research had pointed toward melatonin’s protective cardiovascular effects. This new study challenges common practices around long-term melatonin use for chronic insomnia.
She stressed that melatonin isn’t an FDA-approved treatment for chronic insomnia in the United States. Many people use it this way anyway because it’s available over the counter.
Dr. Ni raised concerns about supplement regulation. The FDA doesn’t regulate melatonin supplements. This means product quality and actual melatonin content can vary widely between brands. Some products might contain much more or less melatonin than the label claims.
He also pointed out that many people taking melatonin might have undiagnosed sleep apnea. This condition involves repeated breathing interruptions during sleep. Sleep apnea itself increases heart disease risk. People might think they just need a sleep aid when they actually need treatment for sleep apnea.
What You Should Do Now
Don’t immediately stop taking melatonin if you’re using it short-term. The increased risk appears connected to long-term use (over one year).
But do consider alternatives for better sleep. Many non-supplement strategies work well. Good sleep hygiene includes keeping a consistent sleep schedule, making your bedroom dark and cool, and avoiding screens before bed.
Regular physical activity during the day helps most people sleep better at night. Just avoid intense exercise close to bedtime.
Watch what you eat and drink in the evening. Caffeine stays in your system for hours. Heavy meals close to bedtime can disrupt sleep. Alcohol might help you fall asleep initially but often causes you to wake up later.
If you struggle with sleep quality, see your doctor. Don’t assume you just need a supplement. Get tested for sleep apnea if you snore, wake up gasping, or feel tired despite sleeping enough hours.
Talk to your healthcare provider before using melatonin long-term. This is especially important if you have existing heart conditions. Your cardiologist should know about any supplements you take regularly.
If you want to track your overall health, tools like those available at HealthCalculator.org can help you monitor various health metrics.
The Bottom Line on Melatonin and Heart Failure
The relationship between melatonin and heart failure isn’t straightforward. New research raises concerns about long-term use. But other studies show potential benefits.
The study presented in November 2025 found that using melatonin for over a year increased heart failure risk by 90%. Users were also more likely to be hospitalized and had higher death rates from any cause.
These findings are significant. But they’re not the final word. The research hasn’t been peer-reviewed. It can’t prove melatonin directly causes these problems. Many confounding factors might explain the association.
Previous research points in the opposite direction. Systematic reviews found melatonin improved outcomes in heart failure patients. Laboratory studies show protective cardiovascular effects through antioxidant and anti-inflammatory properties.
The truth probably lies somewhere in the middle. Melatonin might help some people and harm others. Individual factors like underlying health conditions, dosage, duration of use, and product quality all matter.
More research is definitely needed. Randomized controlled trials would help determine if there’s a real cause-and-effect relationship. Scientists need to understand the biological mechanisms that might link long-term melatonin use to heart problems.
Until then, caution makes sense. Use melatonin thoughtfully, not automatically. Keep it short-term when possible. Focus on addressing the root causes of poor sleep rather than just treating symptoms with supplements.
And remember that “natural” doesn’t always mean risk-free. Melatonin is a hormone that affects multiple body systems. Like any substance that changes how your body works, it deserves respect and careful use.
Disclaimer- This article is for informational purposes only and does not constitute medical advice. The information about melatonin and heart failure is based on current research but should not replace consultation with a qualified healthcare provider. If you have heart conditions, take medications, or use melatonin supplements, talk to your doctor before making any changes. Always seek professional medical advice for health concerns.