Melatonin and Heart Failure: What the Study Found

No study has shown that melatonin causes heart failure or raises your chance of developing it. One 2025 conference abstract of 130,828 adults with insomnia found heart failure in 4.6% of long-term melatonin users versus 2.7% of matched non-users over 5 years¹. It was a records study, presented without full peer review, and it cannot separate melatonin from the insomnia it was taken for².

Randomized trials in people who already have heart disease found no harm and some small, inconsistent improvements from melatonin, including 24 weeks of nightly use in heart failure^{3, 4}. The open question is multi-year use, which no trial has tested. For the condition itself, see our heart failure page.

The study, led by Ekenedilichukwu Nnadi at SUNY Downstate, searched the TriNetX network of electronic health records for adults with an insomnia diagnosis¹. The melatonin group needed at least 1 melatonin prescription and at least 365 days of recorded use. The comparison group had no melatonin recorded anywhere¹.

People with earlier heart failure, or a prescription for another sleeping pill, were left out. Each of the 65,414 users was matched to a non-user on more than 40 factors, including age, sex, other illnesses, heart medicines and blood pressure¹. The average age was 55.7 years and 61.4% were women².

Over the 5 years after matching, the results were¹:

• New heart failure diagnosis: 3,021 users (4.6%) versus 1,797 non-users (2.7%), a hazard ratio of 1.89. The absolute difference was 1.9 percentage points.
• Hospital stay for heart failure: 19.0% versus 6.6%, a hazard ratio of 3.44.
• Death from any cause (all-cause mortality): 7.8% compared with 4.3%, nearly double (hazard ratio 2.09).
• Stricter definition of use (2 or more fills at least 90 days apart): the heart failure hazard ratio was 1.82.

The "90% higher risk" in the headlines is the relative figure. In absolute terms, 1.9 extra cases per 100 users means roughly 1 extra diagnosis for every 53 long-term users over 5 years, if the link were causal¹. Heart failure, which affects about 6.7 million US adults, means the heart can't pump enough oxygen-rich blood for the organs to work properly².

Was the study peer-reviewed?

No. It was a research abstract at the American Heart Association's Scientific Sessions in November 2025. The association notes that such abstracts are not peer-reviewed and count as preliminary until published as a full paper². A 2026 review still described it as a single conference abstract without independent validation⁵.

The researchers themselves said the study cannot prove cause and effect². Researchers writing in Open Heart in 2026 added that melatonin studies are unusually prone to confounding, reverse causation and mislabelled exposure, because who takes melatonin depends on how badly they sleep and how often they see a doctor⁶. Five problems stand out:

• Many non-users were probably users. Only melatonin entered in the medical record counted. Anyone buying it over the counter in the US would have landed in the comparison group².
• Country was unknown. Melatonin needs a prescription in the UK but not in the US, and the data did not record which country each patient lived in².
• Key confounders were missing. The data held nothing on insomnia severity, depression, anxiety or other psychiatric conditions².
• Hospital codes were loose. More people were coded for heart failure hospital stays than for new diagnoses, because hospitals use a range of related codes².
• Some sleep-drug signals are not specific. In 14 years of UK Biobank data on people with insomnia, benzodiazepine users had more heart failure, heart disease and cardiovascular deaths, while Z-drugs showed no link to heart disease, stroke or cardiovascular death⁷. Different sleep drugs carry different signals, and records studies of sleep medicines partly measure who needs them⁶.

Insomnia itself is tied to heart failure

Poor sleep is a heart failure risk factor on its own. In 52,273 UK Biobank adults, people who usually had insomnia had a 39% higher risk of new heart failure (hazard ratio 1.39)⁸. A US survey of 10,432 adults found insomnia linked to 5 times the odds of heart failure, and a genetic analysis in the same paper pointed to a causal role for sleeplessness⁹.

The arrow also runs the other way. Sleep disturbances are common in people with heart failure⁹, so early, undiagnosed heart trouble could prompt someone to start melatonin before the diagnosis is made⁶.

Is there a biological explanation?

None has been shown. One 2026 paper proposed that melatonin might raise prolactin, a hormone whose fragment damages the heart in peripartum cardiomyopathy. Its authors called the idea speculative and unconfirmed⁵. A letter in the Journal of Pineal Research argued that the study's alarm overlooked confounders and the wider safety literature¹⁰.

The rest of the evidence shows no sign of harm, and a possible small benefit in people who already have heart disease. Nothing yet covers years of use.

• US population data: in national survey data from 1999 to 2018, people who had recently used melatonin were no more likely to already have heart disease or heart failure. This was a snapshot survey, so it can't show new cases⁶.
• A trial in heart failure: 92 people with reduced ejection fraction took 10 mg of melatonin or placebo every night for 24 weeks. The melatonin group had lower NT-proBNP (a heart strain marker), better quality of life and better symptom class; other measures did not differ³.
• A 2025 meta-analysis of 4 trials in heart failure: ejection fraction rose 2.39 points, which was not statistically significant, while quality of life improved¹¹.
• A 2026 meta-analysis of 14 trials with 1,027 people with heart disease: the change in ejection fraction (heart pumping function) favoured melatonin by 3.95 points, mostly after bypass surgery, but final ejection fraction, troponin and heart attack size did not consistently improve⁴.

These trials were small and lasted weeks to months^{3, 4}, so they can't rule out a slow effect over 5 years. They do make a strong direct effect on the heart less likely. Our heart health hub covers supplements with better cardiac evidence.

Controlled-release melatonin can lower nighttime blood pressure slightly, but melatonin raised blood pressure in one trial of people taking nifedipine^{12, 13}.

• Controlled-release melatonin: a 2011 meta-analysis of 7 trials (221 people) found no overall effect, but in the 3 controlled-release trials, mostly as an add-on to blood pressure medicine, nighttime systolic pressure fell 6.1 mmHg and diastolic 3.5 mmHg. Fast-release melatonin had no effect¹².
• A later meta-analysis of 4 trials found a 3.57 mmHg drop in systolic pressure during sleep that was not statistically significant, and rated the evidence low to very low¹⁴.
• Untreated high blood pressure: in 16 men, 2.5 mg nightly for 3 weeks cut sleeping blood pressure by 6/4 mmHg and did not change heart rate¹⁵.
• With nifedipine: in 47 people whose blood pressure was controlled on this calcium channel blocker, 5 mg of melatonin at night for 4 weeks raised systolic pressure by 6.5 mmHg, diastolic by 4.9 mmHg and heart rate by 3.9 beats per minute¹³.
• On the label: the licensed 2 mg prolonged-release melatonin (Circadin) lists raised blood pressure as an uncommon side effect¹⁶.

If you treat high blood pressure, check your home readings for a few weeks after starting melatonin.

Can melatonin cause heart palpitations?

Palpitations are uncommon. The label for the licensed 2 mg prolonged-release melatonin (Circadin) lists palpitations as a rare side effect and raised blood pressure as an uncommon one¹⁶. Trial reviews mostly report mild effects such as dizziness, headache, nausea and sleepiness¹⁷. Heart rate rose by 3.9 beats per minute only in the nifedipine trial¹³. In US poison-centre calls about melatonin, mostly for children 5 and under who swallowed it by accident, 83% had no symptoms; among those who did, stomach, heart and nervous-system symptoms were the most common¹⁸.

There is no trial evidence that melatonin treats palpitations either. Our heart palpitations page covers causes and what has been tested.

Can melatonin cause a heart attack?

No study we found links it to heart attacks. The 2025 abstract reported heart failure, heart failure hospital stays and deaths, not heart attacks¹. In trials giving melatonin around a heart attack, effects on heart muscle damage were mixed and depended on timing⁴.

Nobody knows for sure. The National Institutes of Health says short-term melatonin appears safe for most people, but data on long-term safety are lacking¹⁸. A 2016 safety review found that longer randomized trials reported only mild side effects, similar to placebo¹⁷.

"Long-term" in the heart failure study meant at least 365 days of recorded use¹. Most melatonin trials are far shorter: the heart failure trial above ran 24 weeks³.

Mostly because it is a weak fit for chronic insomnia, the reason most people take it for years. The American Academy of Sleep Medicine and the American College of Physicians found too little evidence to recommend it for chronic insomnia. The physicians' guideline recommends cognitive behavioural therapy for insomnia (CBT-I) first¹⁸.

Responding to the 2025 study, an American Heart Association sleep expert said melatonin is not indicated for insomnia in the US and should not be taken chronically without a proper reason². Label accuracy is the other worry, covered below.

There is no agreed maximum, and the heart trials used 2.5-10 mg a night^{15, 13, 3}. A 2022 review of 79 trials of 10 mg or more (3,861 adults) found no detectable rise in serious adverse events in the 4 low-bias trials it could pool (rate ratio 0.88)¹⁹. Minor effects such as drowsiness, headache and dizziness were 40% more common (rate ratio 1.40)¹⁹.

The review's authors called the evidence limited and asked for better long-term safety reporting¹⁹. Use the lowest dose that works. Our melatonin for falling asleep page covers the doses tested for sleep.

Is 5 mg of melatonin very strong?

5 mg is a moderate dose: more than twice the 2 mg dose of the melatonin licensed as a prescription medicine in the UK¹⁶, but half the 10 mg level a 2022 safety review treated as high-dose¹⁹. Use a lower dose if it works for you. The bigger issue is whether the bottle holds 5 mg at all:

• 31 supplements tested in 2017: content ranged from 83% below to 478% above the label, more than 71% missed the label by over 10%, and 26% contained serotonin²⁰.
• 110 US products marketed for children: content ranged from 0% to 667% of the label, and servings held 0.042 to 50 mg²¹.
• 25 US gummies tested in 2023: 22 were mislabelled, with 74% to 347% of the stated dose in those that contained melatonin¹⁸.

Drowsiness and dizziness are among the minor effects seen at higher doses¹⁹. Melatonin can stay active longer in older people and cause daytime drowsiness¹⁸.

These groups should check with a doctor or pharmacist before taking melatonin, or before continuing it long term:

• People with heart failure or heart disease: short trials found small benefits rather than harm^{3, 4}, but nothing covers years of use. Tell your cardiology team you take it.
• People on calcium channel blockers such as nifedipine: blood pressure and heart rate rose in a crossover trial¹³.
• People on blood thinners or with epilepsy: the NIH advises medical supervision¹⁸.
• Pregnant or breastfeeding women: there is too little research on safety^{18, 17}.
• People with dementia: sleep medicine guidelines recommend against melatonin for them¹⁸.
• People on other medicines: the NIH advises anyone on medicine to ask first¹⁸. Avoid melatonin with the antidepressant fluvoxamine, which raises melatonin levels about 17-fold¹⁶. If you take an antidepressant, see SSRIs and supplements.

Not necessarily. The 2025 study looked only at people with insomnia who used melatonin for a year or more¹. Match your situation:

• Short-term use, such as jet lag or a few rough weeks: the study doesn't apply. See melatonin for jet lag for timing and doses.
• Nightly for more than a year for insomnia: ask your doctor about CBT-I, which guidelines put first¹⁸. Untreated insomnia is itself linked to heart failure⁸. Our melatonin for insomnia page sets out what the trials show.
• You have heart failure: the one trial in heart failure used 10 mg nightly for 24 weeks, and the melatonin group did better than placebo³. Keep your care team informed rather than starting or stopping on your own.
• You're on blood pressure medicine: check readings after starting, especially with nifedipine¹³.
• Any use: choose the lowest dose that works, since labels can be far off²⁰.

Comparing other options? Our guide to sleep supplements covers the alternatives, and the insomnia page covers the condition itself.

Related conditions

• Heart Failure
• Insomnia
• Heart Palpitations
• Elevated Blood Pressure

We searched PubMed and a research-paper index for melatonin with heart failure, blood pressure, heart rate and long-term safety. We read the original Circulation abstract, the American Heart Association's release on it and the NIH's melatonin fact sheet. We read 19 journal records and 4 web pages, including the UK label for prescription melatonin, and cited 18 records and 3 pages. We gave most weight to randomized trials and meta-analyses, and treated records studies as hypothesis-generating.

As of October 14, 2026, we found no full peer-reviewed paper of the 2025 heart failure study. No randomized trial has followed melatonin users for years, so long-term heart safety remains unknown.

1. Nnadi E, et al. Abstract 4371606: Effect of Long-term Melatonin Supplementation on Incidence of Heart Failure in Patients with Insomnia. Circulation. 2025;152(Suppl_3). doi:10.1161/circ.152.suppl_3.4371606
2. American Heart Association Newsroom. Long-term use of melatonin supplements to support sleep may have negative health effects (Scientific Sessions 2025, abstract MP2306). November 3, 2025. https://newsroom.heart.org/news/long-term-use-of-melatonin-supplements-to-support-sleep-may-have-negative-health-effects
3. Hoseini SG, et al. Melatonin supplementation improves N-terminal pro-B-type natriuretic peptide levels and quality of life in patients with heart failure with reduced ejection fraction: Results from MeHR trial, a randomized clinical trial. Clin Cardiol. 2022;45(4):417-426. doi:10.1002/clc.23796
4. Ang SP, et al. Melatonin Supplementation and Cardiovascular Outcomes: A Systematic Review and Meta-Analysis of Randomized Trials. J Clin Med. 2026;15(9). doi:10.3390/jcm15093444
5. Savvidis C, et al. Melatonin supplementation, hyperprolactinemia, and incident heart failure: A proposed prolactin-mediated pathway for cardiovascular risk. World J Exp Med. 2026;16(2):120754. doi:10.5493/wjem.v16.i2.120754
6. Khan B, et al. Melatonin and cardiovascular risk: an NHANES reality check after recent heart failure concerns. Open Heart. 2026;13(1). doi:10.1136/openhrt-2026-004108
7. Xie Y, et al. Hypnotic use and the risk of cardiovascular diseases in insomnia patients. Eur J Prev Cardiol. 2025;32(6):466-474. doi:10.1093/eurjpc/zwae263
8. Fei M, et al. Association of insomnia and its proteomic signatures with incident heart failure: A European population-based study. Sleep Health. 2026;12(2):340-348. doi:10.1016/j.sleh.2025.12.009
9. Wang J, et al. Sleep disturbances and heart failure: observational study and Mendelian randomization study. Arch Med Sci. 2025;21(4):1222-1232. doi:10.5114/aoms/194883
10. Colitta A, et al. Navigating Melatonin Safety: Fact, Fiction, and Confounders. J Pineal Res. 2026;78(2):e70129. doi:10.1111/jpi.70129
11. Daliri AS, et al. Melatonin as a Novel Drug to Improve Cardiac Function and Quality of Life in Heart Failure Patients: A Systematic Review and Meta-Analysis. Clin Cardiol. 2025;48(3):e70107. doi:10.1002/clc.70107
12. Grossman E, et al. Effect of melatonin on nocturnal blood pressure: meta-analysis of randomized controlled trials. Vasc Health Risk Manag. 2011;7:577-84. doi:10.2147/VHRM.S24603
13. Lusardi P, et al. Cardiovascular effects of melatonin in hypertensive patients well controlled by nifedipine: a 24-hour study. Br J Clin Pharmacol. 2000;49(5):423-7. doi:10.1046/j.1365-2125.2000.00195.x
14. Lee EK, et al. Controlled-release oral melatonin supplementation for hypertension and nocturnal hypertension: A systematic review and meta-analysis. J Clin Hypertens (Greenwich). 2022;24(5):529-535. doi:10.1111/jch.14482
15. Scheer FA, et al. Daily nighttime melatonin reduces blood pressure in male patients with essential hypertension. Hypertension. 2004;43(2):192-7. doi:10.1161/01.HYP.0000113293.15186.3b
16. Circadin 2 mg Prolonged-release Tablets: Summary of Product Characteristics (SmPC). Electronic Medicines Compendium (emc). Last updated February 11, 2025. https://www.medicines.org.uk/emc/product/2809/smpc
17. Andersen LP, et al. The Safety of Melatonin in Humans. Clin Drug Investig. 2016;36(3):169-75. doi:10.1007/s40261-015-0368-5
18. National Center for Complementary and Integrative Health (NIH). Melatonin: What You Need To Know. Last updated May 2024. https://www.nccih.nih.gov/health/melatonin-what-you-need-to-know
19. Menczel Schrire Z, et al. Safety of higher doses of melatonin in adults: A systematic review and meta-analysis. J Pineal Res. 2022;72(2):e12782. doi:10.1111/jpi.12782
20. Erland LA, et al. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content. J Clin Sleep Med. 2017;13(2):275-281. doi:10.5664/jcsm.6462
21. Pawar RS, et al. A Survey of Melatonin in Dietary Supplement Products Sold in the United States. Drug Test Anal. 2025;17(8):1176-1185. doi:10.1002/dta.3823