Melatonin and Heart Failure: What the Research Says

The melatonin heart-failure headlines, in plain terms

Melatonin and heart failure landed in the news in late 2025, when a preliminary study reported that adults who took melatonin nightly for a year or more had higher rates of heart failure. That finding needs a careful read, and this page gives one: what it does and does not mean.

Melatonin is a hormone your brain already makes to time sleep. In the United States it is sold over the counter as a dietary supplement, and it is one of the most common sleep aids people buy. Because it is a supplement and not a prescription drug, it never goes through the Food and Drug Administration review that medications do. The headline claim is worth taking seriously. The question underneath it is about long-term nightly use, not the occasional tablet before a red-eye flight.

Does melatonin cause heart failure?

Melatonin has not been shown to cause heart failure. The 2025 research found an association, and the researchers said it cannot prove cause and effect, because a records-based study cannot fully separate the supplement from the people taking it, who tend to have chronic insomnia that carries its own heart risk.

That last point does most of the work. Clinicians call it confounding by indication: the reason someone takes a treatment is itself tied to the outcome being measured. People who take melatonin nightly for years are not a random group. They have chronic insomnia, and insomnia on its own is linked to higher cardiovascular risk, including a roughly 40% higher chance of developing or dying from cardiovascular disease. Genetic research points the same way, tying a predisposition to insomnia to higher odds of heart failure. So when a records study sees more heart failure among long-term melatonin users, some of that gap may belong to the sleeplessness itself.

Proving cause would take a different kind of study, one that follows people forward and assigns melatonin or a placebo at random. That work has not been done, and no regulator has warned against melatonin on heart grounds. “Not proven to be harmful” is not the same as “proven to be safe,” and the sections below sit honestly in that gap.

What the melatonin heart-failure study found

The melatonin heart-failure study found that adults with chronic insomnia who took melatonin for at least a year had about a 90% higher rate of new heart failure over five years than similar people who did not. It was presented as a preliminary abstract at a cardiology meeting and has not been peer-reviewed.

Here is what sits behind that number. Researchers reviewed the health records of roughly 130,000 adults with insomnia, comparing long-term melatonin users with matched non-users. Over five years, the American Heart Association reported from its 2025 Scientific Sessions, new heart failure showed up in 4.6% of the melatonin group and 2.7% of the others. The abstract also reported more heart-failure hospitalizations and more deaths among the melatonin users. Those figures are why melatonin got linked to heart failure across so many headlines.

The abstract came with clear limits, which its authors named plainly. This is the kind of study that can show a pattern but cannot prove cause. It had no data on melatonin dose. In some records, over-the-counter melatonin was not captured at all, so the melatonin group was probably undercounted. And it lacked information on how severe each person’s insomnia was, or whether depression or anxiety was in the picture, which can shape both sleep-aid use and heart health. It was presented in November 2025 and had not been published in a peer-reviewed journal since.

What earlier research said about melatonin and the heart

Before this abstract, a body of research ran the other way. A 2022 review of melatonin in cardiovascular disease described it as possibly protective, pointing to antioxidant activity, modest blood-pressure lowering, and anti-inflammatory effects, and noting that small trials in heart patients had turned up no harm signal. That review leaned mostly on laboratory and animal work plus a handful of small human studies, and its authors were clear that larger clinical trials are needed before anyone calls melatonin good for the heart.

Both pictures can be true, because they answer different questions. A short-term effect on blood vessels in a lab is a separate matter from swallowing a supplement nightly for years. The fair summary is that the evidence is mixed and mostly low-quality on both sides. One preliminary abstract does not erase years of earlier work, and that work does not wave away a new safety question. What is left is genuine uncertainty, which is where a careful decision starts.

Long-term melatonin safety and who should be careful

Melatonin is not right for everyone, and its long-term side effects are not well studied. People with existing heart failure or heart disease, older adults, and anyone taking blood-pressure medicines or blood thinners should check with a clinician before using it nightly, because melatonin can interact with those medicines.

Its known short-term effects are usually mild, including headache, dizziness, nausea, and next-day grogginess, according to the National Center for Complementary and Integrative Health. The bigger unknown is what taking it nightly for years does, because that research simply is not there yet.

The supplement label adds a second problem. Because melatonin is not regulated like a drug, the amount in a bottle often misses what the label claims. One analysis found melatonin content ranging from about 83% below to 478% above the labeled amount across products, with some also containing serotonin. A third-party quality seal, such as USP verification, is one way to narrow that gap. “Natural” does not make a nightly hormone risk-free.

A few groups have more reason to be cautious and should talk with a clinician before using melatonin regularly:

• People with existing heart failure or heart disease
• Older adults
• Anyone taking blood-pressure medications or blood thinners, since melatonin can interact with them
• People on other interacting medicines, including immunosuppressants, diabetes medicines, and seizure medicines

The every-night-for-years habit, in these groups especially, is what the current safety questions are really about.

If you take melatonin now, what to rely on for sleep

There is no need to stop cold after one preliminary study. But if melatonin has become a nightly habit with no end in sight, that is worth raising with a clinician, and the more useful question is why sleep is still broken.

Most coverage skips one piece of context. Melatonin’s evidence is strongest for shifting the timing of sleep, such as jet lag or a delayed body clock. It does much less for ongoing insomnia, which is why sleep medicine guidelines do not recommend melatonin for chronic insomnia. What they do recommend, as the first-line treatment, is cognitive behavioral therapy for insomnia, or CBT-I: a short, structured program that retrains the habits and thoughts keeping sleep broken, and it outperforms sleep aids over time. When insomnia travels with anxiety or depression, treating the mood condition often loosens the sleep problem too. If you are weighing supplements, our piece on magnesium for sleep and anxiety covers another common option. To sort out the underlying chronic insomnia with a professional, medication management and an evaluation are the place to start.

When broken sleep needs an evaluation

Trouble sleeping at least three nights a week for three months or more is the clinical line for chronic insomnia, and it is worth an evaluation instead of another year of self-treatment. So is trouble getting through the day, however long it’s lasted, or noticing that a nightly supplement has quietly become the only thing getting you to sleep. Reach out sooner if you snore or gasp awake, which can point to sleep apnea, or if low mood or anxiety is riding along. An evaluation looks at your sleep pattern, your health and medications, and any mood symptoms, then matches a plan to the cause. Zellig Psychiatry offers in-person care and secure video visits statewide across Pennsylvania; current in-person options are on our locations page.

Frequently asked questions

This is general information, not medical advice. Decisions about your own melatonin use, medications, or sleep belong with your prescriber.