Melatonin sits at a fascinating crossroads between sleep biology and heart health. It’s a hormone your brain releases at night to help coordinate your circadian rhythm (your internal 24-hour clock). Heart failure, meanwhile, is not just a “pump problem”—it’s also a condition shaped by inflammation, oxidative stress, the autonomic nervous system (fight-or-flight vs. rest-and-digest), and disrupted sleep. Because melatonin influences several of those pathways, researchers have been studying whether it could help heart failure… while recent large database findings have also raised the question of whether long-term melatonin use might be associated with a higher risk of developing heart failure in certain populations.

So what’s the real link? It’s best described as: melatonin biology and heart failure are connected, but melatonin supplementation is still an evidence-mixed area where context matters.

 

1) Why Melatonin is Relevant to Heart Failure in the First Place

Melatonin is the body’s “night signal”

Melatonin secretion is controlled by a brain timing system that responds to light and darkness. At night, melatonin rises; in the morning, it falls. This rhythmic signal helps coordinate sleep timing, body temperature, blood pressure patterns, and aspects of immune and metabolic function.

Heart failure is tightly tied to circadian disruption

People with heart failure commonly experience sleep disruption (insomnia, fragmented sleep, sleep-disordered breathing), and heart failure itself can disturb day–night patterns in hormones and autonomic activity. Research reviews have also found that abnormal melatonin patterns or lower melatonin levels are associated with worse prognosis in heart failure, suggesting melatonin rhythm may act as a marker of overall physiologic strain.

In plain terms: when the heart is struggling, the whole “nighttime repair system” often struggles too.

 

2) Potential “Protective” Mechanisms: How Melatonin Could Theoretically Help in Heart Failure

A lot of melatonin enthusiasm comes from biology and early clinical signals:

Antioxidant and mitochondrial support

Heart failure involves high oxidative stress and impaired energy production in heart muscle cells. Melatonin has been described in the scientific literature as having antioxidant and mitochondria-supporting effects, which could theoretically protect cardiac tissue and improve cellular efficiency.

Autonomic nervous system effects (less “fight-or-flight” at night)

Many heart failure patients have elevated sympathetic (“fight-or-flight”) activity, which can worsen heart strain over time. Melatonin may influence autonomic balance and nighttime blood pressure regulation—important because abnormal nocturnal blood pressure patterns are linked to cardiovascular risk.

Endothelial function and vascular effects

Endothelial dysfunction (poor blood-vessel lining function) is common in heart failure and contributes to symptoms and disease progression. A recent systematic review of circadian rhythm/melatonin in heart failure notes small human supplementation studies reporting improvements in measures such as endothelial function, BNP (a heart failure biomarker), and quality of life with melatonin dosing in heart failure patients—though the evidence base is limited.

Key nuance: These “benefit” signals tend to come from small, controlled studies with defined doses and monitored patients—not from long-term, real-world over-the-counter use across broad populations.

 

3) The New Concern: Long-Term Melatonin use Associated with Higher Heart Failure Risk (observational data)

In late 2025, reports from the American Heart Association Scientific Sessions highlighted a large, multinational cohort analysis (using the TriNetX research network) suggesting that in adults with chronic insomnia, long-term melatonin use was associated with:

  • higher hazard of incident heart failure,
  • more heart failure hospitalizations,
  • and higher all-cause mortality over several years.

This finding has been widely covered—with many experts emphasizing caution in interpretation because association is not causation, and conference-presented observational work can have important limitations.

Why an observational “signal” might appear even if melatonin isn’t the cause

Several plausible explanations exist:

  • Confounding by indication: People taking melatonin long-term may have more severe insomnia, anxiety, depression, chronic illness, or lifestyle factors that also raise heart failure risk.
  • Reverse causation: Early, undiagnosed cardiovascular changes can worsen sleep; melatonin use may be a marker that something else was already developing.
  • Dose and product variability: Especially where melatonin is over-the-counter, dose and purity can vary—meaning “melatonin use” in a database is not the same as a consistent, controlled medication exposure.
  • Missing data: Many people buy melatonin OTC without it appearing in medical records, which can blur “user vs. non-user” comparisons.

The bottom line: the signal is important and worth further study, but it does not prove melatonin causes heart failure.

 

4) How Both Things Can Be True: Possible Benefit in HF Patients vs. Possible Risk in Long-Term Insomnia Use

This is the heart of the confusion, and it’s common in medicine:

  • In small trials of heart failure patients, melatonin may improve certain biomarkers or vascular function under controlled conditions.
  • In large real-world cohorts of insomnia patients, long-term melatonin use may correlate with worse outcomes, potentially reflecting confounding, different populations, different durations, and different dosing/product quality.

These are not automatically contradictory findings—they may simply be studying different questions.

 

5) Safety and Medication Considerations for People with Heart Failure

If you have heart failure (or high cardiovascular risk) and are considering melatonin, the safest approach is: treat it like a real drug, not a harmless vitamin.

Points to discuss with a clinician:

  • Blood pressure and heart rate effects: Melatonin can influence nighttime BP patterns; this may or may not be desirable depending on your medications and baseline blood pressure regulation.
  • Drug interactions: Some references caution about potential interactions with commonly used cardiovascular medications (for example, anticoagulants/blood thinners and certain blood pressure drugs), and clinicians typically advise individualized review.
  • Sleep problems that need targeted treatment: In heart failure, insomnia may be driven by nocturnal symptoms, fluid shifts, anxiety, restless legs, or sleep apnea—treating the cause often matters more than adding a sleep aid.

 

6) Practical Guidance: What People Searching “Melatonin and Heart Failure” Should Do

If you already have heart failure

  • Don’t start long-term melatonin on your own as a nightly habit.
  • If you want to try it, consider it a short-term, low-dose experiment under guidance—especially if you’re on anticoagulants, sedatives, or complex cardiovascular regimens.
  • Ask your clinician specifically about screening for sleep apnea (very common in HF), because treating apnea can improve symptoms and outcomes more directly than supplements.

If you do NOT have heart failure but use melatonin nightly for insomnia

  • The recent observational signal is a reason to reassess chronic nightly use, not panic.
  • Consider non-supplement approaches with better long-term evidence for chronic insomnia (like CBT-I, light timing, consistent sleep window, and reducing late-night screen light exposure).

If you use melatonin occasionally

Short-term use for circadian misalignment (jet lag, shift changes) is generally treated as a different scenario than “every night for years.” The newer risk signal specifically concerns long-term regular use in insomnia cohorts.

 

Takeaway

The melatonin–heart failure link isn’t a simple “good” or “bad.” Heart failure and circadian biology are closely intertwined, and melatonin has plausible mechanisms (and limited early clinical signals) for benefit in monitored settings.  At the same time, large real-world observational data presented in 2025 raise concerns that long-term melatonin use in chronic insomnia patients is associated with higher heart failure risk and worse outcomes, though causality is unproven and confounding is likely.

 

Heart Aid

 

READ MORE: Beetroot Juice and Blood Pressure: How New Research Reveals Powerful Benefits for Older Adults


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