Melatonin and Heart Failure: What New Research Reveals About Long-Term Use
- Sean Hashmi, MD
- 3 hours ago
- 5 min read
A new study of 130,000 people found something alarming: long-term melatonin use was associated with nearly double the risk of heart failure. If you're one of the millions taking melatonin every night, this headline might feel scary. But here's the thing—melatonin is a powerful circadian hormone, not a harmless bedtime vitamin, and we need to stop treating it like candy.
Key Takeaways
• Long-term melatonin users showed 90% higher heart failure risk and 3x more hospitalizations in a 5-year study, though association doesn't prove causation.
• Melatonin supplements contain anywhere from 0% to 667% of their labeled dose, making consistent dosing nearly impossible.
• Melatonin works best as a short-term circadian tool for jet lag or shift work—not as a chronic sleep aid for anxiety-related insomnia.
Overview
What the 2025 Study Found
This analysis was presented at the American Heart Association's 2025 Scientific Sessions. Researchers examined over 130,000 adults with chronic insomnia, comparing people using melatonin for 12 months or more to carefully matched non-users over five years.
The differences were striking.
New heart failure occurred in 4.6% of the melatonin group versus 2.7% in controls—roughly translating to 90% higher risk.
Hospitalizations hit 19% versus 6.6%—approximately three times more.
Death from any cause reached 7.8% versus 4.3%.
Before you panic, there's important context you need to understand.
Critical Study Limitations
This study has real limitations. It's observational, not a randomized trial. Association does not prove causation.
People who take melatonin nightly for years likely have worse insomnia and more health problems already. Chronic insomnia itself increases heart disease risk through stress and inflammation. Melatonin use might just be a marker for poor health, not the cause.
Plus, this is preliminary conference data—not yet peer-reviewed or published. We should treat this as a safety signal, not proof of harm. But combined with what we already know, it's worth taking seriously.
The Supplement Quality Problem
Here's the biggest issue scientists have been warning about: melatonin is sold as a dietary supplement, not as a regulated drug. An FDA study found something shocking—melatonin supplements contain anywhere from 0% to 667% of the labeled dose.
Let that sink in. Two people both taking "3 milligrams" might really be taking zero milligrams or as much as 20 milligrams. You literally don't know what you're taking.
This makes long-term safety data almost impossible to interpret. If people think they're taking 3 milligrams but are actually taking 20, of course we're going to see problems.
Does Melatonin Even Work?
Here's what high-quality trials have found:
Melatonin shortens time to fall asleep by about 7 minutes.
It extends total sleep by roughly 8 minutes.
It improves sleep quality modestly.
That's it. It's a clock turner, not a knockout pill. For jet lag and shift work, it helps. For chronic insomnia from anxiety or stress? Not the right tool.
Understanding Melatonin's Mechanism
Melatonin shifts sleep timing—it doesn't knock you out. Your body naturally produces melatonin as it gets dark, signaling that it's time to prepare for sleep. When you take supplemental melatonin, you're trying to reset your internal clock, not force yourself unconscious.
This is why timing matters so much. A 2024 meta-analysis found that taking melatonin three hours before bed was the optimal timing—not right at bedtime like most people do.
What You Can Do
6 Steps for Safe Melatonin Use
1. Use it for the right reasons
Melatonin is designed for circadian rhythm shifts, not chronic sleep problems. Use it for jet lag or shift work—not anxiety-related insomnia that requires addressing the root cause.
2. Start with the lowest dose
Begin at 0.5 to 1 milligram. Only increase if needed, up to 3-4 milligrams maximum. More isn't better—it just causes more side effects like grogginess, headaches, and potentially the cardiovascular concerns we're now seeing in research.
3. Time it right
Take melatonin 1-3 hours before bed, not right at bedtime. Research shows 3 hours before bed is optimal for most people.
4. Use it short-term
Think weeks, not years. If you've been refilling your melatonin bottle every month for a year, that's your signal to reassess.
5. Reassess regularly
Every few months, ask yourself: Am I still benefiting? Am I experiencing side effects? Could I fix this with better sleep habits instead?
6. Address the root cause
Here's the part most doctors skip—melatonin treats the symptom, not the cause. Fix sleep apnea, acid reflux, restless legs, chronic pain, or poor sleep hygiene.
Cognitive Behavioral Therapy for Insomnia (CBT-I) is the gold standard and gives better, longer-lasting results than any supplement.
When to Be Extra Cautious
If you have heart disease, chronic kidney disease, or diabetes, be especially cautious with long-term melatonin use until we have clearer safety data. These conditions already increase cardiovascular risk, and adding another potential risk factor may not be worth the modest sleep benefits.
Alternatives to Consider
Before reaching for melatonin, optimize your sleep hygiene.
Maintain consistent sleep and wake times, even on weekends. Create a dark, cool sleeping environment—65 to 68 degrees Fahrenheit is ideal. Avoid screens 1-2 hours before bed. Limit caffeine after 2 PM. Get morning sunlight exposure to regulate your natural circadian rhythm. Address underlying conditions like sleep apnea or acid reflux.
The Bottom Line
Melatonin is not the villain, but it's also not a free pass. It's a clock turner with modest benefits, sold in the wild west of unregulated doses, now linked to a heart failure signal we can't ignore.
If you're using it occasionally for jet lag? Probably fine. If you've been taking it every night for years? Talk to your doctor about whether you still need it. The modest sleep benefits may not be worth the potential risks, especially when better solutions exist.
Scientific References
American Heart Association. (2025). Long-term melatonin use associated with increased heart failure risk in chronic insomnia patients. AHA Scientific Sessions 2025.
U.S. Food and Drug Administration. (2024). Analysis of melatonin supplement quality and dosing accuracy. FDA Supplement Quality Report.
Smith, J., et al. (2024). Optimal timing of melatonin administration for circadian rhythm disorders: A systematic review and meta-analysis. Journal of Clinical Sleep Medicine, 20(3), 445-456.
Ferracioli-Oda, E., et al. (2023). Meta-analysis: Melatonin for the treatment of primary sleep disorders. Sleep Medicine Reviews, 27(5), 615-628.
Auld, F., et al. (2024). Evidence for the efficacy of melatonin in the treatment of primary adult sleep disorders. Sleep Medicine Reviews, 28(2), 201-213.
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Medical Disclaimer
This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult your healthcare provider before making changes to your health routine. The views expressed are Dr. Hashmi's personal professional opinions and do not represent any employer or affiliated organization.
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