“A large study presented in November 2025 linked a year or more of recorded melatonin use in adults with insomnia to more heart failure over five years: 4.6% versus 2.7% in matched non-users. It was observational and shared as a meeting abstract, so it shows an association, not proof that melatonin harms the heart. The link between melatonin and heart failure is still an open question, which is why anyone with heart disease, or anyone taking melatonin nightly for months, should check with a doctor.”
If you take melatonin most nights, the headlines about melatonin and heart failure probably stopped you cold. "90% higher risk" is a frightening phrase, and it spread fast in November 2025.
Here's what the study actually measured, with the exact numbers and the limits spelled out in the American Heart Association's news release. Then comes what's been published since, what's known about long-term use and who should talk to a doctor first.
Fact 1: What the melatonin and heart failure study found
The research was presented at the American Heart Association's Scientific Sessions 2025 in New Orleans as Abstract MP2306. The AHA summed it up in a news release on November 3, 2025. The lead author was Ekenedilichukwu Nnadi, M.D., chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn.
The team used the TriNetX Global Research Network, a large international database of de-identified electronic health records. They pulled five years of records for 130,828 adults with insomnia. The average age was 55.7, and 61.4% were women.
Long-term use had a specific meaning: a year or more of melatonin documented in a person's health record. In all, 65,414 people met that bar. The comparison group also had insomnia but never had melatonin recorded anywhere in their charts.
The two groups were matched on 40 factors, including age, sex, race and ethnicity, heart and nervous system conditions, the medicines for them, blood pressure and body mass index. Anyone who already had heart failure, or had been prescribed other sleeping pills such as benzodiazepines, was left out.
Here is what the release reports over the five years:
- New heart failure: 4.6% of long-term melatonin users versus 2.7% of matched non-users, about a 90% higher chance.
- Hospital stays for heart failure: users were nearly 3.5 times as likely to be hospitalized for it (19.0% versus 6.6%).
- Death from any cause: 7.8% versus 4.3%, nearly twice as likely.
- A stricter check: when the melatonin group was limited to people with at least two prescriptions filled at least 90 days apart, the heart failure result was similar, at 82% higher.
What 4.6% versus 2.7% means in real numbers
Relative risk often sounds bigger than absolute risk. Over five years, 4.6% versus 2.7% works out to about 46 versus 27 people out of every 1,000. (The release's "90% higher" and "3.5 times" figures come from the researchers' statistical analysis, not a simple division of the percentages.) That gap is worth taking seriously, and it also means most people in both groups did not develop heart failure during the study.
One number looks odd: more people were hospitalized for heart failure (19.0%) than were newly diagnosed with it (4.6%). The release explains that a hospital stay can carry a range of related diagnostic codes that don't always include the code for a new heart failure diagnosis, so the two figures aren't directly comparable.
Heart failure doesn't mean the heart has stopped. The NHLBI describes it as a condition in which the heart doesn't pump enough blood for the body's needs. It's serious and needs medical care, and it usually follows another problem that has damaged the heart, such as coronary heart disease or high blood pressure. The AHA's release puts the number of U.S. adults living with it at 6.7 million.
Fact 2: A link isn't proof that melatonin causes heart failure
Does melatonin cause heart failure? This study can't answer that, and its authors say so plainly. Nnadi said in the release that "our study cannot prove a direct cause-and-effect relationship," adding: "This means more research is needed to test melatonin's safety for the heart."
The reason is the design. In an observational study, researchers look back at what happened to people who made their own choices. Nobody was randomly assigned to melatonin or a placebo, so the two groups can differ in ways that matching on 40 factors doesn't capture.
Nnadi named some possible culprits: "Worse insomnia, depression/anxiety or the use of other sleep-enhancing medicines might be linked to both melatonin use and heart risk." The researchers didn't have information on how severe each person's insomnia was or on other psychiatric conditions, so they couldn't adjust for them.
That matters because the reason someone reaches for melatonin can carry heart risk of its own. If people with the worst, longest-lasting insomnia are the ones with a year of melatonin in their charts, the supplement could simply be a marker of that group. The study can't tell the two explanations apart, which is why the question of melatonin and heart failure stays open.
Fact 3: Who counted as a melatonin user changes the picture
The first limitation the release lists is how melatonin use was recorded. TriNetX includes countries where melatonin needs a prescription, such as the United Kingdom, and countries where it's sold over the counter, such as the United States. Patient locations weren't part of the data the researchers could see.
Use was identified only from medication entries in health records. So, as the release itself notes, people taking over-the-counter melatonin in the U.S. or other countries without a prescription rule would have landed in the non-melatonin group. Some of the "non-users" were probably users, which blurs the comparison.
The melatonin group may be unusual too. Marie-Pierre St-Onge, Ph.D., a Columbia University sleep researcher who chaired the writing group for an AHA scientific statement on sleep health and wasn't involved in the study, said she was surprised that physicians would prescribe melatonin for insomnia for more than 365 days. She pointed out that in the U.S., melatonin isn't indicated for the treatment of insomnia. So people with a year of recorded melatonin may not resemble someone who takes a gummy now and then.
Finally, it was a meeting abstract. The AHA notes that abstracts presented at its meetings aren't peer reviewed and that findings are considered preliminary until they're published as a full paper in a peer-reviewed journal. When we checked in late October 2026, we couldn't find a full peer-reviewed version of this study.
Fact 4: What's been published since November 2025
The most direct follow-up we found is a peer-reviewed analysis published in May 2026 in Open Heart, a BMJ journal. Two Vanderbilt University researchers looked at melatonin use in a national U.S. health survey, the National Health and Nutrition Examination Survey (NHANES), from 1999 to 2018.
Melatonin users in that survey looked very different from non-users before heart outcomes even entered the picture. They were far more likely to report sleep problems (57.9% versus 20.5%) and depression (13.3% versus 5.5%). That's the kind of gap that makes melatonin studies hard to read.
After adjusting for age, sex, race and ethnicity, body mass index, smoking, high blood pressure and diabetes, recent melatonin use was not significantly linked to cardiovascular disease or heart failure. The authors are careful not to oversell it. Only 267 of the more than 50,000 adults analyzed reported recent melatonin use, so the estimates are imprecise. NHANES only captured melatonin use in the past 30 days, not years of nightly use, and it counted heart conditions people already had at the time of the survey rather than new cases over time. They call their result a hypothesis-generating counterpoint, not proof of safety.
They also spell out why research on melatonin and heart failure is so tricky:
- The reason for taking it. People start melatonin because of insomnia, stress, depression or anxiety, conditions tied to heart risk on their own.
- Reverse causation. Early, undiagnosed heart problems can disturb sleep and prompt someone to start melatonin, so the supplement appears to come first.
- Missing use. Over-the-counter melatonin isn't always captured in medication lists or surveys, and dose and duration are often missing.
Their conclusion: the observational data don't establish definitive heart harm, and they don't establish safety either. The two studies also asked different questions, long-term recorded use in people with insomnia versus recent use in the general population. For clinicians, they advise documenting over-the-counter use and putting the underlying sleep problem first.
Fact 5: Long-term melatonin use has thin safety data
Set the heart headlines aside, and the honest summary of long-term melatonin use is "we don't know enough." According to NCCIH, short-term use appears to be safe for most people, but information on long-term safety is lacking, and the possible long-term side effects are unclear. Short-term studies in adults mostly reported mild effects such as headache, dizziness, nausea and sleepiness.
The NHLBI adds two points worth weighing when you think about melatonin's long-term effects. Research has not proven that melatonin is an effective treatment for insomnia, and melatonin can affect your body's control of blood pressure, causing high or low blood pressure. Its listed side effects also include daytime sleepiness, headaches, upset stomach and worsening depression.
Guidelines line up with that. NCCIH notes that sleep medicine and physician groups found too little strong evidence to recommend melatonin for chronic insomnia, and that cognitive behavioral therapy for insomnia (CBT-I) is the strongly recommended first step. For children there's even less long-term information: because melatonin is a hormone, NCCIH says it's possible it could affect hormonal development, including puberty, but nobody knows for sure.
Product quality adds uncertainty. In the U.S., melatonin is sold as a dietary supplement, which NCCIH says is regulated less strictly than prescription or over-the-counter drugs. In a 2017 test of 31 melatonin supplements, most didn't contain the amount on the label, and 26% contained serotonin. For a broader look at what melatonin can do day to day, see melatonin side effects.
The AHA release doesn't mention doses or forms, so it can't tell you whether tablets, gummies or a melatonin sleep spray carry different risks. For dose questions, our guide to whether 10mg of melatonin is too much covers the details.
Is it safe to take melatonin every night?
For a few weeks, most healthy adults seem to tolerate it. For months or years, nobody can promise much, because the long-term data are thin. St-Onge's advice in the AHA release was that people should be aware that melatonin "should not be taken chronically without a proper indication."
If you've reached for it most nights for months, that's a good reason to ask your doctor what's keeping you awake. Our guide to whether melatonin is addictive covers habit, tolerance and how to step back from it.
Is melatonin bad for your heart? Who should check with a doctor
There's no proof that melatonin damages the heart. But "not proven harmful" isn't the same as "proven safe for years," and some people have more reason to ask before taking it night after night:
- You have heart disease or heart failure, or you've been told you're at high risk of either.
- You take blood pressure medicine. NHLBI notes melatonin can push blood pressure up or down.
- You take a blood thinner or have epilepsy. NCCIH says people in both groups need medical supervision when taking melatonin.
- You've taken melatonin most nights for months, whatever the reason.
- You're pregnant or breastfeeding, or you're an older adult. NCCIH notes a lack of safety research in pregnancy and breastfeeding, and that melatonin may stay active longer in older people and cause daytime drowsiness.
- You drink in the evening. Alcohol and sleep aids are a poor mix; see melatonin and alcohol.
If your melatonin was prescribed, talk to the prescriber before you stop or change it. Melatonin is prescription-only in some countries, including the United Kingdom, and the doctor who prescribed it can weigh your heart history against the reason you take it. Don't stop, start or change a prescription because of a headline.
Symptoms that need a doctor, melatonin or not
- Signs of heart trouble. NHLBI lists feeling tired and short of breath, and fluid buildup in the lower body, around the stomach or in the neck. Call 911 for chest pain or sudden, severe trouble breathing.
- Insomnia that won't quit. Trouble sleeping on most nights for three months or more, or tiredness that gets in the way of your day.
- Breathing problems in sleep. Loud snoring, gasping or pauses in breathing can point to sleep apnea.
- Low mood. If you feel hopeless or have thoughts of harming yourself, contact a doctor, or in the US call or text 988.
At a glance: melatonin and heart failure in numbers
The study: 130,828 adults with insomnia · TriNetX health records · long-term use meant 12 months or more of melatonin on record.
Over five years: new heart failure 4.6% vs. 2.7% · heart failure hospital stays 19.0% vs. 6.6% · deaths from any cause 7.8% vs. 4.3%.
The catch: observational, so an association, not cause · a meeting abstract, not peer reviewed · over-the-counter users likely counted as non-users.
Your next step: no need to panic · prescribed melatonin, talk to the prescriber first · heart disease or nightly use for months, ask your doctor.
If you'd rather skip nightly melatonin: where Adapt X.1 fits
Some readers come away from this study wanting a break from nightly melatonin, at least until better evidence arrives. If that's you, Adapt X.1 is one option to discuss with your doctor. It's a melatonin-free sleep spray built on a single plant active, Zea mays extract (an extract of natural grasses, 60 mg per serving prior to micronization), plus purified water and natural mint. That's the whole label.
To be clear about what we're not saying: we make no heart-health claims for Adapt X.1, and switching sleep aids isn't a heart-health strategy. What it offers is a different approach for people who would rather not take melatonin night after night. There's no melatonin and no sedative in it, and it's non-habit forming.
You take 6 to 10 sprays (0.75 ml) in your mouth about 30 minutes before sleep, then swallow. It was studied in a double-blind, placebo-controlled clinical trial. In that trial, participants fell asleep 33% faster than with placebo, spent 24% more time in REM sleep and had 30% fewer wake-ups in the night. Individual results vary.
With nothing sedating in it, there's no grogginess to sleep off. Many people notice an easier wind-down on the first night, and most feel their rhythm settle between weeks two and four of nightly use. A single bottle covers 30 nights, and the 60-night money-back guarantee gives you time to see how it suits you.
If you have a medical condition, consult a professional before use. If you have heart disease, take blood pressure or blood-thinning medicines, are pregnant or breastfeeding, or take other medicines (especially sleep medicines), ask your doctor or pharmacist first, and talk to them before combining sleep aids, including supplements.
Questions people ask
Does melatonin cause heart failure?
There's no proof that it does. The 2025 study linked long-term melatonin use in people with insomnia to more heart failure, but it was observational and couldn't separate melatonin from the insomnia, depression or other conditions that led people to take it. A 2026 national survey analysis found no significant link with recent use. Randomized trials are the clearest way to settle cause and effect.
I've taken melatonin for years. Should I stop?
If it was prescribed, don't stop or change it without talking to your prescriber. If you buy it yourself, there's no emergency, but it's a good moment to ask your doctor whether you still need it, especially if you have heart disease or take blood pressure or blood-thinning medicines. Ask about the sleep problem underneath too, since CBT-I is the recommended first step for chronic insomnia.
Should my doctor know I take melatonin?
Yes. Mention it, along with any other supplement, at every visit and to your pharmacist. The Open Heart authors specifically advise clinicians to document over-the-counter melatonin use, because it isn't always captured in medical records.
Does melatonin raise blood pressure?
It can move it in either direction. NHLBI notes that melatonin can affect your body's control of blood pressure, causing high or low readings. If you take blood pressure medicine, ask your doctor or pharmacist before using melatonin.
The bottom line
The melatonin and heart failure headlines came from a real but preliminary finding. In health records of adults with insomnia, a year or more of recorded melatonin use went along with more heart failure, more hospital stays and more deaths over five years. The study can't show that melatonin caused any of it, and a 2026 national survey analysis found no significant link with recent use.
So don't panic, and don't ignore it either. Long-term safety data for melatonin are thin. If you have heart disease, take blood pressure or blood-thinning medicines, or have used melatonin nightly for months, talk to your doctor. If it was prescribed, don't change anything without your prescriber.