If you searched melatonin and heart failure after a headline caught your eye, here is the short answer: a 2025 study linked long-term melatonin use to higher rates of heart failure in adults with insomnia. The study cannot show that melatonin causes the problem, and the wider research on melatonin and the heart is mixed. This page walks through what the study found, what it cannot prove, and what your options look like.
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What did the 2025 melatonin heart failure study find?
The study was presented as preliminary findings at the American Heart Association’s Scientific Sessions 2025. Cardiocaretoday’s report gives its main numbers.
It looked at 130,828 adults with insomnia. Their average age was 55, and 61% were women. The researchers drew the data from electronic health records in the TriNetX database.
Of those adults, 65,414 had been prescribed melatonin at least once and had taken it for at least one year. Each was compared with a matched group of people who had never been prescribed melatonin. The groups were matched on 40 factors, such as demographics, health conditions and medications. People who already had heart failure, or who took other sleeping pills, were left out.
Over five years, the reported outcomes were:
| Outcome over 5 years | Long-term melatonin users | Never prescribed melatonin |
|---|---|---|
| Developed heart failure | 4.6% | 2.7% |
| Hospitalized for heart failure | 19.0% | 6.6% |
| Died from any cause | 7.8% | 4.3% |
The “90% higher risk” figure is the headline number. Cardiocaretoday reports that users had about a 90% higher chance of developing heart failure over five years. National Geographic quotes cardiologist Shaline Rao with the same figure, for users who took melatonin for a year or longer.
The study is observational, so it does not prove cause. Lead author Ekenedilichukwu Nnadi said, “our study cannot prove a direct cause-and-effect relationship.” He also noted that worse insomnia, depression or anxiety, or other sleep medicines could be linked to both melatonin use and heart risk.
Cardiocaretoday’s report gives the all-cause mortality figures: 7.8% for long-term melatonin users and 4.3% for those never prescribed melatonin.
Is melatonin bad for your heart?
The research is mixed, and that is the most accurate answer right now. National Geographic’s December 2025 explainer lays out both sides. Some studies point to modest benefits, such as lower blood pressure at night. Other studies raise concerns, including higher blood pressure in otherwise healthy adults and higher risks of heart failure. Some find little or no measurable effect.
Research on melatonin specifically for heart failure is thin. A 2018 review in Molecules says “few clinical studies have investigated the role of melatonin in the context of heart failure.” A 2025 meta-analysis in Clinical Cardiology pooled just four articles. It found better quality-of-life scores and lower fatigue. Its change in ejection fraction was not statistically significant (p = 0.27).
On the other side, Clyde Yancy, a former president of the American Heart Association, cited a 2022 systematic review. That review found “no consistent benefit on blood pressure, coronary artery disease, or cardiac function.”
Melatonin may also interact with heart medicines. National Geographic reports evidence that it may interfere with calcium-channel blockers, potentially blunting their blood pressure-lowering effects. If you take one of these, raise it with your clinician before you start.
Is there a new warning on melatonin, and why do some doctors avoid it?
The new attention comes from that preliminary study, which was presented at a conference. Melatonin is still widely used. National Geographic says it is “generally considered safe for short-term use and may be appropriate for some individuals under medical guidance.”
Some clinicians decline to recommend it. Eleanor Levin, a clinical professor of medicine at Stanford, told National Geographic she does not recommend or prescribe it because of observational studies linking it to heart failure.
What happens if you take melatonin every night, and what if you stop?
The 2025 study looked at people who took melatonin for a year or longer. It measured use over that span, not the effect of any single night.
National Geographic quotes Yancy on duration: “The duration of therapy should be limited to less than three months.” The introduction to a PubMed Central magnesium trial says melatonin is “a widely used dietary supplement for sleep regulation,” but that its “long-term efficacy and safety remain in question.”
If you already take it nightly, ask your clinician what long-term use means for your sleep and heart, and what to expect if you stop.
Do melatonin pills work for sleep?
Cleveland Clinic says melatonin “can partially help manage your body’s sleep-wake cycle.” It adds that melatonin “works best if you’re a night owl and have a delayed circadian rhythm.” The same article urges a full evaluation of sleep problems before you turn to supplements.
Rao says shift workers, people who often have jet lag, and people with delayed sleep-wake phase disorder may all benefit from melatonin for their circadian rhythm.
What is the safest sleep aid to take?
No single sleep aid is the safest for everyone. The clearest starting point in these sources is behavioral. Cleveland Clinic calls cognitive behavioral therapy for insomnia (CBT-I) “a first-line treatment.” It says CBT-I “tends to have much better long-term outcomes than using a sleep aid or a sleep medication.”
| Option | What the sources say | Who it suits and the limits |
|---|---|---|
| CBT-I (behavioral therapy) | A PubMed Central magnesium trial says CBT-I “is considered the most effective treatment for chronic insomnia.” Cleveland Clinic calls it first-line. | Usually delivered through a clinician or program. The NHS sleep advice notes treatments available from a GP or pharmacist. |
| Prescription sleep medicines (benzodiazepines, zolpidem, zaleplon) | Can give short-term relief, with risks of “dependence, tolerance and next-day cognitive or motor impairment, especially with prolonged use” | Prescribed by a clinician. The risks grow with prolonged use. |
| Antihistamines such as diphenhydramine (over the counter) | More accessible for occasional sleep disturbances, but “rapid tolerance and next-day sedation limit their daily use in people reporting only mild insomnia” | Best suited to occasional use. Next-day sleepiness is the main limit. |
| Melatonin (over-the-counter supplement) | National Geographic says it is generally considered safe for short-term use. The introduction to a PubMed Central magnesium trial says its long-term efficacy and safety “remain in question.” | Heart disease and heart or blood pressure medicines call for a clinician conversation first. |
| Magnesium (supplement) | Cleveland Clinic says magnesium “may help some people sleep better, but there’s still not enough research to know how well it works.” | May interact with some antibiotics, osteoporosis medicines and diuretics. See the best time to take magnesium glycinate guide for timing and safety. |
| Sleep habits | The NHS says “making small changes to habits and routines that help you sleep can make a real difference.” Cleveland Clinic lists a consistent sleep schedule, limiting caffeine and alcohol, and a cool, dark bedroom. | Low cost and low risk, and a good base for any other option. |
Prices change, so check current prices with your pharmacy or the product label. For a broader look at supplements for better sleep, see our overview.
Can 10 mg of melatonin cause diarrhea?
The melatonin studies above name heart effects, not diarrhea. National Geographic notes that dose, timing and formulation all change how melatonin behaves in the cardiovascular system. Diarrhea is the side effect Cleveland Clinic lists for magnesium, not melatonin. It says taking more than 350 mg per day from supplements can cause diarrhea, nausea and stomach cramps.
For a 10 mg melatonin dose, your pharmacist can check the strength on your label against the other medicines you take.
What should you check on a melatonin gummy label?
Cardiocaretoday notes that “over-the-counter melatonin supplements are unregulated, meaning each brand’s supplements vary in potency and purity.” Rao advises “choosing products independently tested by reputable third parties.” Check the strength on the label of any gummy or pill, and look for third-party testing before you buy.
Does melatonin lower your body’s own production?
Your body makes melatonin mainly in the pineal gland in the brain. The studies above do not say whether taking a supplement lowers that natural output. Ask your clinician whether a supplement makes sense for your sleep pattern.
Which organ does melatonin affect?
The brain is where melatonin is made and where its sleep-regulating role is best known. National Geographic says melatonin receptors “are concentrated in the brain’s circadian centers” and “are also found throughout cardiovascular tissues, including in blood vessels and heart muscle.”
Can your heart affect your sleep?
The NHLBI says heart failure may eventually cause tiredness and shortness of breath. Its heart failure research page describes the CONCERT-HF trial, which tested cells taken from a patient’s bone marrow and heart and injected into the heart. The NHLBI describes that trial as measuring emotional symptoms, including trouble sleeping. That is a measure in one trial, not a general heart failure symptom.
In the other direction, Healthline reports that a lack of sleep may pose “adverse psychological and physiological effects,” including an “increased risk of heart disease, diabetes, and obesity.”
What are some organizations that focus on heart disease?
As of November 2026, the NHLBI’s heart failure overview says heart failure “is a condition that develops when your heart doesn’t pump enough blood for your body’s needs.” It adds that heart failure “is a serious condition that has no cure,” and that treatment can help many people have a higher quality of life.
- NHLBI (National Heart, Lung, and Blood Institute) funds heart research and runs The Heart Truth, which raises awareness about heart disease in women.
- American Heart Association hosted the 2025 Scientific Sessions where the melatonin study was presented.
- Centers for Disease Control and Prevention is the source the NHLBI cites for the number of U.S. adults with heart failure, more than 6 million.
What is still unknown about melatonin and the heart?
- Cause. The study’s authors say it cannot show cause, and they call for more research.
- Standardized trials. NYU Langone cardiologist Doris Chan says the field needs “large randomized controlled trials that use standardized doses and formulations, follow participants over extended periods, and account for underlying health conditions and medication use.”
- Who is affected. Heart disease, other medicines and other health conditions may change how melatonin affects a given person.
Before you decide
- Tell your clinician or pharmacist your sleep problem, your heart history and every medicine you take, including blood pressure medicines.
- Ask whether melatonin fits your sleep pattern, and whether CBT-I or another option should come first.
- Ask what a 10 mg dose would mean for you, and what to expect if you stop after long-term use.
- Check the strength on the label of any melatonin gummy or pill, and look for third-party testing.
- If you saw a different melatonin study, such as one attributed to MIT, search its title on PubMed and read the abstract. The 2025 melatonin heart failure meta-analysis is an example of what a PubMed record contains.
The headline is a reason to ask questions, not a verdict on melatonin for everyone. Bring this study to your clinician and weigh it against your sleep history and your heart health.
By the Clinical Research Explained Editorial Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.