Sleep, The Endocrine System
Melatonin Supplements and Risks
Potential risks associated with long-term melatonin use among adults with chronic insomnia were highlighted in a recent preliminary study presented at the American Heart Association’s Scientific Sessions 2025
Led by Dr. Ekenedilichukwu Nnadi, a chief resident at SUNY Downstate Health Sciences University, the observational analysis examined over 130,000 patients, half of whom had documented chronic melatonin use (defined as a year or longer, including prescriptions or self-reported). None had prior heart failure or used prescription sleep aids at baseline.
Key findings include a 90% increased relative risk of developing heart failure within five years for long-term users (4.6% incidence vs. 2.7% in non-users), a 3.5-fold higher likelihood of heart failure hospitalization (19% vs. 6.6%), and nearly double the all-cause mortality rate (7.8% vs. 4.3%). ahajournals.org
The study emphasizes association rather than causation. Chronic insomnia itself may contribute to these effects through inflammation, elevated nighttime blood pressure, or stress hormone dysregulation. newsroom.heart.org
The research highlights regulatory gaps: U.S. melatonin supplements are unregulated, with actual doses varying significantly (up to +478% or -83% from the labels), unlike the stricter prescription-only rules in the UK, EU, and Australia. nytimes.com
Nnadi cautions against assuming “natural” equals safe, especially for nightly, multi-year use.
He calls for randomized trials to clarify mechanisms, such as their impact on heart rhythm or metabolism.
Experts like Columbia University’s Marie-Pierre St-Onge note melatonin’s lack of FDA approval for chronic insomnia treatment and urge short-term use only. washingtonpost.com
Sleep specialist Dr. Muhammad A. Rishi recommends starting with 0.5–1 mg doses, limiting the duration to 1–3 months, and consulting a physician for persistent issues, as insomnia may signal underlying conditions such as sleep apnea or depression.
The Council for Responsible Nutrition echoes this, advising that professional guidance is necessary for long-term sleep troubles.
New Details from Additional Research
While the study raises alarms, it aligns with growing scrutiny of melatonin’s real-world safety.
Hazard ratios from the abstract confirm the risks: 1.90 for incident heart failure, 3.47 for hospitalization, and 1.80 for mortality, even after adjusting for confounders like age, comorbidities, and multiple prescriptions. ahajournals.org
Confounding factors—such as users having more severe insomnia, co-occurring depression/anxiety, or polypharmacy with other sedatives—could explain much of the link. newsroom.heart.org
Contrasting evidence suggests that melatonin’s antioxidant properties may benefit individuals with established heart disease. A 2023 meta-analysis of 10 trials (n=1,200) found that short-term use (up to 3 months) reduced systolic blood pressure by 3.5 mmHg and improved endothelial function in hypertensive patients.
Animal studies suggest cardioprotective effects against ischemia-reperfusion injury, but human data is limited to small, controlled settings with pharmaceutical-grade doses—not the variable OTC products in Nnadi’s cohort.
Recent U.S. trends amplify concerns: CDC data shows melatonin-related emergency visits rose 530% from 2019–2022, often from overdoses or accidental ingestion, particularly in children.
A 2024 FDA warning highlighted inaccurate labeling in 25% of tested supplements, potentially leading to unintended high exposures that disrupt natural hormone rhythms over time.
Experts urge caution without panic: NBC reports cardiologists view chronic use as a “red flag” for unmanaged insomnia rather than melatonin toxicity, recommending cognitive behavioral therapy for insomnia (CBT-I) as first-line treatment, which cuts heart risks by 40% in meta-analyses. nbcnews.com
For at-risk groups (e.g., those with hypertension), monitoring heart rate variability via wearables during use is recommended.
Led by Dr. Ekenedilichukwu Nnadi, a chief resident at SUNY Downstate Health Sciences University, the observational analysis examined over 130,000 patients, half of whom had documented chronic melatonin use (defined as a year or longer, including prescriptions or self-reported). None had prior heart failure or used prescription sleep aids at baseline.
Key findings include a 90% increased relative risk of developing heart failure within five years for long-term users (4.6% incidence vs. 2.7% in non-users), a 3.5-fold higher likelihood of heart failure hospitalization (19% vs. 6.6%), and nearly double the all-cause mortality rate (7.8% vs. 4.3%). ahajournals.org
The study emphasizes association rather than causation. Chronic insomnia itself may contribute to these effects through inflammation, elevated nighttime blood pressure, or stress hormone dysregulation. newsroom.heart.org
The research highlights regulatory gaps: U.S. melatonin supplements are unregulated, with actual doses varying significantly (up to +478% or -83% from the labels), unlike the stricter prescription-only rules in the UK, EU, and Australia. nytimes.com
Nnadi cautions against assuming “natural” equals safe, especially for nightly, multi-year use.
He calls for randomized trials to clarify mechanisms, such as their impact on heart rhythm or metabolism.
Experts like Columbia University’s Marie-Pierre St-Onge note melatonin’s lack of FDA approval for chronic insomnia treatment and urge short-term use only. washingtonpost.com
Sleep specialist Dr. Muhammad A. Rishi recommends starting with 0.5–1 mg doses, limiting the duration to 1–3 months, and consulting a physician for persistent issues, as insomnia may signal underlying conditions such as sleep apnea or depression.
The Council for Responsible Nutrition echoes this, advising that professional guidance is necessary for long-term sleep troubles.
New Details from Additional Research
While the study raises alarms, it aligns with growing scrutiny of melatonin’s real-world safety.
Hazard ratios from the abstract confirm the risks: 1.90 for incident heart failure, 3.47 for hospitalization, and 1.80 for mortality, even after adjusting for confounders like age, comorbidities, and multiple prescriptions. ahajournals.org
Confounding factors—such as users having more severe insomnia, co-occurring depression/anxiety, or polypharmacy with other sedatives—could explain much of the link. newsroom.heart.org
Contrasting evidence suggests that melatonin’s antioxidant properties may benefit individuals with established heart disease. A 2023 meta-analysis of 10 trials (n=1,200) found that short-term use (up to 3 months) reduced systolic blood pressure by 3.5 mmHg and improved endothelial function in hypertensive patients.
Animal studies suggest cardioprotective effects against ischemia-reperfusion injury, but human data is limited to small, controlled settings with pharmaceutical-grade doses—not the variable OTC products in Nnadi’s cohort.
Recent U.S. trends amplify concerns: CDC data shows melatonin-related emergency visits rose 530% from 2019–2022, often from overdoses or accidental ingestion, particularly in children.
A 2024 FDA warning highlighted inaccurate labeling in 25% of tested supplements, potentially leading to unintended high exposures that disrupt natural hormone rhythms over time.
Experts urge caution without panic: NBC reports cardiologists view chronic use as a “red flag” for unmanaged insomnia rather than melatonin toxicity, recommending cognitive behavioral therapy for insomnia (CBT-I) as first-line treatment, which cuts heart risks by 40% in meta-analyses. nbcnews.com
For at-risk groups (e.g., those with hypertension), monitoring heart rate variability via wearables during use is recommended.
Read
What stimulates normal melatonin secretion in the human body?
Sources
- American Heart Association. “Long-term use of melatonin supplements to support sleep may have negative health effects.” November 2025. https://newsroom.heart.org/news/long-term-use-of-melatonin-supplements-to-support-sleep-may-have-negative-health-effects
- Nnadi, E. et al. “Abstract 4371606: Effect of Long-term Melatonin Supplementation on Incident Heart Failure, Heart Failure Hospitalization, and All-Cause Mortality in Adults With Insomnia.” Circulation. November 2025. https://www.ahajournals.org/doi/abs/10.1161/circ.152.suppl_3.4371606
- NBC News. “What taking melatonin could reveal about your heart health.” November 2025. https://www.nbcnews.com/health/health-news/taking-melatonin-reveal-heart-health-rcna241132
- News-Medical.net. “Long-term use of melatonin supplements linked to higher risk of heart failure and death.” November 2025. https://www.news-medical.net/news/20251103/Long-term-use-of-melatonin-supplements-linked-to-higher-risk-of-heart-failure-and-death.aspx
- The New York Times. “Is Melatonin Bad for Your Heart? Here’s What to Know.” November 2025. https://www.nytimes.com/2025/11/05/well/melatonin-heart-health-study.html
- The Washington Post. “New study links melatonin and heart failure. Don’t panic, experts say.” November 2025. https://www.washingtonpost.com/health/2025/11/03/melatonin-heart-failure-sleep-aid/
- Drugs.com. “Long-Term Melatonin Use for Insomnia Tied to Higher Risk for Heart Failure, Death.” November 2025. https://www.drugs.com/news/aha-long-term-melatonin-insomnia-tied-higher-risk-heart-failure-127448.html
- Powers Health. “Long-Term Melatonin Might Harm Heart Health, Study Says.” November 2025. https://www.powershealth.org/about-us/newsroom/health-library/2025/11/03/longterm-melatonin-might-harm-heart-health-study-says
- Wang, Y. et al. “Effects of melatonin supplementation on blood pressure: A systematic review and meta-analysis.” Hypertension Research. 2023. https://www.nature.com/articles/s41440-023-01275-5
- Cardinali, D. et al. “Melatonin and cardioprotection against ischemia/reperfusion injury.” Antioxidants. 2022. https://www.mdpi.com/2076-3921/11/3/543
- CDC. “Notes from the Field: Melatonin Poisoning — United States, 2019–2022.” MMWR. 2024. https://www.cdc.gov/mmwr/volumes/73/wr/mm7306a3.htm
- Irish, L. et al. “The role of sleep hygiene in promoting public health: A review of empirical evidence.” Sleep Medicine Reviews. 2015. https://www.sciencedirect.com/science/article/pii/S1087079214001255
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