Millions of people keep a bottle of melatonin on their nightstand like it’s as benign as a glass of warm milk. It’s sold without a prescription in nearly every pharmacy and grocery store across the country. The label calls it “natural.” The marketing calls it “safe.” And for most people, it feels like a sensible, harmless choice when sleep just won’t come.
But something about that picture may be more complicated than it seems. Sleep troubles and heart health have a long and tangled relationship, one that researchers have been working to understand for years. Now, a large new analysis has raised a question that very few people were asking: could taking melatonin night after night, month after month, actually be connected to something as serious as heart failure?
The findings are preliminary, and the researchers themselves are careful about what they mean. Still, the numbers are striking enough that heart specialists, sleep experts, and cardiologists are paying close attention. If you take melatonin regularly – or know someone who does – this is worth reading carefully.
What the Study Actually Found
A preliminary study presented at the American Heart Association’s Scientific Sessions 2025 found that adults with chronic insomnia who used melatonin for a year or longer were more likely to develop heart failure, be hospitalized for heart failure, and die from any cause than those who did not take the supplement.
The research team, led by Dr. Ekenedilichukwu Nnadi of SUNY Downstate/Kings County, used data from the TriNetX Global Research Network to assess melatonin use in 130,828 adults diagnosed with insomnia. Of those participants, with an average age of 56 years and 61% women, 65,414 had been prescribed melatonin at least once and reported taking it for at least one year.
Each melatonin user was carefully matched to a non-user, with researchers accounting for demographics, 15 different health conditions, heart-related medications, lab results, vital signs, and healthcare use. The goal was to isolate, as much as possible, the difference that melatonin use might make.
Participants who used melatonin for more than one year increased their heart failure risk by 90% over five years, compared to those not using melatonin. To put that in plain terms: out of every 100 people with insomnia who took melatonin long-term, roughly 4.6 developed heart failure, compared to 2.7 out of 100 who didn’t take it.
The hospitalization numbers were even more alarming. Participants taking melatonin were nearly 3.5 times as likely to be hospitalized for heart failure, compared to those not taking melatonin (19.0% vs. 6.6%). Scientists also found that participants taking melatonin were about twice as likely to die from any cause over the five-year follow-up period, compared to those not taking the supplement.
Of note, patients with prior heart failure or those taking other prescription sleep medications were excluded from the study, which strengthens the relevance of the findings somewhat, though it doesn’t remove the uncertainty.
A Supplement Taken by Millions
To understand why this study matters, you need to know just how many people are reaching for melatonin. The use of melatonin supplements by adults in the United States more than quintupled between 1999 and 2018, according to the NIH. Melatonin use climbed from 0.4% of survey participants to 2.1% over those nearly two decades, and the use of high doses, defined as over 5 milligrams per day, rose from 2005 onward.
In the United States, it is estimated that as many as 2.1% of adults and 6% of children, totaling over 5 million adults and 4 million children, take melatonin at least monthly. Unlike in many other countries, melatonin is available over the counter in the U.S. and is classified as a dietary supplement by the FDA, meaning it is not subject to the same regulations required of prescription pharmaceuticals.
Melatonin is a hormone produced by the pineal gland that regulates the body’s sleep-wake cycle. Its levels naturally rise in the dark and drop during daylight hours. Synthetic melatonin, which is chemically identical to the natural hormone, is widely used to treat insomnia and jet lag. The “natural” label has helped drive its popularity, but as this study suggests, naturally produced in the body doesn’t necessarily mean safe when taken in supplement form over the long term.
Chronic insomnia affects up to one-third of adults, and while over-the-counter melatonin has increasingly been promoted as a sleep-friendly choice, robust data on its long-term cardiovascular safety have been lacking. Poor sleep and heart health are more closely connected than most people realize – understanding how sleep quality affects your heart and brain is important context for anyone managing a heart condition or persistent insomnia.
Heart Failure Is Already a Serious Public Health Problem
Before going further, it helps to understand what heart failure actually is. According to the American Heart Association’s 2025 Heart Disease and Stroke Statistics, heart failure occurs when the heart cannot pump enough oxygen-rich blood to sustain the body’s organs, and the condition affects about 6.7 million U.S. adults.
It’s a progressive condition. People with heart failure often find themselves short of breath doing tasks they once did easily – climbing stairs, carrying groceries, walking across a parking lot. Many end up hospitalized repeatedly. It’s also one of the leading reasons adults over 65 are admitted to the hospital in the U.S. Given how serious heart failure is, any association with a widely used supplement warrants careful scrutiny.
The connection between poor sleep and heart health is already well established. In the past decade, a number of observational studies have demonstrated an association between insomnia and incident cardiovascular disease, including hypertension, coronary heart disease, and heart failure, according to a review published in the NIH’s PubMed database. Chronic insomnia can elevate stress hormone levels, leading to persistent high blood pressure and increased heart workload. So researchers were already aware that the population most likely to use melatonin long-term – those with chronic insomnia – carries elevated cardiac risk to begin with. That’s exactly what makes this study both valuable and difficult to interpret.
The Critical Caveat: Association Is Not Causation
This is where the story gets more complicated, and where it’s important not to overreact. The findings showed no evidence that melatonin supplements themselves cause heart problems. Rather, the need for melatonin as a sleep aid may hide underlying symptoms of cardiac risk.
The lead researcher was clear about this limitation. “Worse insomnia, depression/anxiety, or the use of other sleep-enhancing medicines might be linked to both melatonin use and heart risk,” Dr. Nnadi said. “Our study cannot prove a direct cause-and-effect relationship.”
Chronic insomnia – a condition shared by all study participants – may itself be a contributing factor to heart health outcomes, raising more questions than answers. In other words, the people who needed melatonin for an entire year or more may have been people with more severe sleep problems to begin with, and severe sleep problems are themselves a risk factor for heart disease.
There’s also a technical limitation worth understanding. The study population was limited to patients with chronic insomnia, comparing those with documented melatonin use for at least a year to those without such records. Because melatonin is sold over the counter in the U.S. and doesn’t require a prescription, as the American Heart Association itself notes, this research represents early, non-peer-reviewed data that cannot establish cause and effect.
The findings are preliminary and were presented at a conference, meaning they have not yet undergone peer review. That’s an important distinction. Conference abstracts are a signal that something deserves more investigation – they’re not a final verdict.
What Sleep Researchers Are Saying
Dr. Marie-Pierre St-Onge, a sleep researcher at Columbia University Irving Medical Center and chair of the AHA’s 2025 statement on sleep health, said she was surprised that physicians would prescribe melatonin for insomnia and have patients use it for more than a year. She said that even though melatonin is available over the counter in the U.S., it shouldn’t be used long term without a clear medical reason.
Melatonin has no FDA-approved indication for treating insomnia in America, and over-the-counter melatonin should not be used chronically without proper medical justification. This is a point many people don’t know: the fact that something is legal to buy without a prescription doesn’t mean a doctor would recommend it as a long-term solution.
Melatonin supplements are not intended to treat chronic insomnia or other sleep disorders. The Council for Responsible Nutrition‘s voluntary melatonin labeling guidelines, adopted in 2024, recommend upper dosage levels and include advisory statements such as “For occasional and/or intermittent use only” and “Consult a healthcare professional if you are experiencing long-term sleep difficulties.”
Read More: Trouble Sleeping? Try One of These Natural Sleep Remedies
What You Should Do Now
The honest takeaway from this research is not “throw away your melatonin tonight.” It’s something more measured than that, but no less important.
If you take melatonin occasionally – for jet lag, a particularly rough night, or adjusting to a new schedule – the evidence does not suggest you’re at risk. Short-term use of melatonin supplements appears to be safe for most people. The concern in this study was specifically about chronic, long-term use in people with persistent insomnia.
If you’ve been taking melatonin every night for months or years, that’s the pattern this research flagged. The most sensible step is to talk to your doctor – not in a panic, but as part of a genuine conversation about why you’re not sleeping well and whether there’s a better solution for your specific situation.
Cognitive behavioral therapy for insomnia (CBT-I) represents an effective non-medication option. Lifestyle modifications, including regular exercise, sleep schedule consistency, and bedroom environment optimization, help many people. Medical evaluation should identify and treat any underlying conditions contributing to sleep problems.
Chronic insomnia that requires a nightly supplement for over a year is, in itself, a sign that something deserves medical attention. The supplement may have been masking the question your body was actually asking. As Dr. Nnadi said: “Melatonin supplements may not be as harmless as commonly assumed. If our study is confirmed, this could affect how doctors counsel patients about sleep aids.”
That’s not a reason to panic. It is a reason to pay attention, ask better questions, and stop treating a nightly melatonin habit as something too minor to mention to your doctor.
Disclaimer: The author is not a licensed medical professional. The information provided is for general informational and educational purposes only and is based on research from publicly available, reputable sources. It is not intended to constitute, and should not be relied upon as, medical advice, diagnosis, or treatment. Always consult a licensed physician or other qualified healthcare provider regarding any medical condition, symptoms, or medications. Do not disregard, avoid, or delay seeking professional medical advice or treatment because of information contained herein.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.
Read More: 10 Weird Signs That May Indicate You’re Sleep-Deprived (Beyond Fatigue)