The Hidden Dangers of Nightly Melatonin

The Hidden Cardiovascular Risks of Long-Term Melatonin Use: What Doctors Need to Know

Melatonin has become one of the world’s most commonly used sleep supplements. Patients take it for everything from mild insomnia to jet lag, night-shift adjustment, anxiety-related sleep issues, and general “sleep enhancement.” Many believe it is harmless because it is “natural,” widely available, and not classified as a prescription drug in many countries.

But new large-scale data reveal something deeply concerning: long-term melatonin use may significantly increase the risk of heart failure, cardiovascular hospitalization, and even death, especially among patients with chronic insomnia.

These new findings challenge long-held assumptions about melatonin’s safety and force clinicians to reconsider how freely this hormone should be recommended for nightly use.

Melatonin: A Hormone, Not Just a Supplement
Melatonin is a naturally occurring hormone produced by the pineal gland. Its main role is to signal nighttime and regulate sleep–wake cycles. But melatonin also interacts with:

• cardiovascular regulation
  
  
• metabolic pathways
  
  
• blood pressure control
  
  
• immune signaling
  
  
• endocrine function
  

Unlike prescription sleep medications, melatonin supplements are often unregulated, inconsistently dosed, and widely assumed to be safe. Patients take them nightly for months or years without medical supervision.

This ease of access and lack of monitoring may have contributed to a sense of safety that is now being challenged by new data.

The New Evidence: Long-Term Melatonin Linked to Heart Failure Risk
Researchers analyzed tens of thousands of individuals diagnosed with chronic insomnia and followed them for five years. Participants who used melatonin every night for at least a year were compared with similar individuals who did not use melatonin.

The findings were alarming:

A 90% Greater Risk of Heart Failure
Individuals taking melatonin long-term had nearly double the risk of developing heart failure compared with non-users. This is not a small signal — it is a large, clinically meaningful association.

3.5 Times Higher Risk of Heart Failure Hospitalization
The same group was more than three times as likely to be hospitalized with heart failure over the five-year follow-up period.

A Twofold Increase in All-Cause Mortality
Long-term melatonin users had approximately double the risk of dying from any cause during the study period.

These numbers are not subtle. They demand attention.

Why These Findings Matter for Clinical Practice
For years, doctors have viewed melatonin as relatively benign — certainly safer than benzodiazepines, Z-drugs, sedating antihistamines, or off-label antidepressants used for sleep.

But this new evidence suggests we may have underestimated melatonin’s physiological effects when used chronically.

A supplement taken casually by children, adults, and the elderly might carry long-term cardiovascular risks we were not aware of.

Understanding the Limitations: Association, Not Proven Causation
It is important to emphasize:

• These studies are observational.
  
  
• They show correlation, not direct proof of causation.
  
  
• People who take melatonin long-term may already differ in meaningful ways from those who don’t.
  

However, even with adjustments for confounding factors — age, BMI, comorbidities, medications — the associations remained strong.

In clinical medicine, when an association is large, consistent, and biologically plausible, it becomes difficult to ignore.

Possible Biological Explanations
The study did not explore mechanisms, but several theories may explain the link between long-term melatonin use and cardiovascular disease.

1. Disruption of Natural Circadian Cardiovascular Rhythms
Melatonin plays a role in controlling nighttime blood pressure. Chronic supplementation may:

• blunt natural circadian variations
  
  
• disrupt autonomic balance
  
  
• worsen nocturnal hypertension
  

Even subtle chronic disruptions can translate into long-term cardiovascular stress.

2. Impact on Hormonal Systems
Melatonin interacts with:

• cortisol secretion
  
  
• reproductive hormones
  
  
• metabolic hormones
  
  
• inflammatory pathways
  

Chronic overexposure might disturb systems that indirectly influence heart failure risk.

3. Sedation Masking Symptoms
Patients using melatonin nightly may overlook early symptoms of:

• fluid overload
  
  
• reduced exercise tolerance
  
  
• arrhythmias
  
  
• nighttime dyspnea
  

This may delay diagnosis of early heart disease.

4. Marker of More Severe Insomnia
Chronic insomnia itself is cardiovascularly harmful. Patients who rely on melatonin nightly may represent those with:

• persistent sympathetic activation
  
  
• chronic stress
  
  
• dysfunctional sleep architecture
  

In this case, melatonin is not causing the disease — but the people who need melatonin may already be higher-risk.

What This Means for Doctors Managing Insomnia
These findings do not mean melatonin should be banned or completely avoided. But they absolutely mean that nightly, long-term, unmonitored use is not something clinicians should automatically endorse.

A. Melatonin should not be the first-line treatment for chronic insomnia
The recommended first-line therapy remains Cognitive Behavioral Therapy for Insomnia (CBT-I), which has far stronger evidence for both safety and effectiveness.

B. Short-Term Use Appears Much Safer Than Long-Term Use
Occasional melatonin use — for a week or two — has not been associated with major harm.
The concern lies with months and years of continuous nightly dosing.

C. Review and Reassess Every Patient Using Melatonin Nightly
Questions to ask:

• How long have you been taking it?
  
  
• What dose?
  
  
• Does it still help?
  
  
• Have we explored alternatives?
  

Many patients continue melatonin simply because it has become a habit.

D. Consider the Patient’s Cardiovascular Risk Profile
Extra caution is appropriate for:

• elderly patients
  
  
• patients with hypertension
  
  
• patients with atrial fibrillation
  
  
• individuals with diabetes
  
  
• people with established cardiovascular disease
  

These groups already have elevated heart failure risk.

E. Teach Sleep Hygiene and Circadian Regulation
Patients often turn to melatonin without addressing the basics:

• consistent sleep schedule
  
  
• controlled evening light exposure
  
  
• reduced evening screen use
  
  
• eliminating caffeine after midday
  
  
• temperature and noise optimization
  
  
• maintaining daytime activity and natural light exposure
  

These strategies often outperform supplements in the long run.

Melatonin Misconceptions That Need Correcting
1. “Natural means safe.”
This is one of the most dangerous assumptions in modern supplement culture. Natural compounds can be potent hormones — melatonin included.

2. “If it’s not working, increase the dose.”
High doses of melatonin may worsen sleep quality, cause daytime sedation, or interact with blood pressure regulation.

3. “You can take melatonin every night forever.”
This new research strongly challenges that idea.

4. “Over-the-counter means harmless.”
In many countries, supplement manufacturing is poorly regulated. Some melatonin products contain:

• far higher doses than stated
  
  
• additional sedative compounds
  
  
• varying purity between batches
  

This variability raises concerns about long-term exposure.

What to Tell Patients Who Already Take Melatonin Long-Term
Many patients reading this will already be taking melatonin nightly. Clinicians should not induce panic but guide patients through a structured plan:

Step 1: Evaluate Necessity
Ask whether the patient still needs it or whether the habit simply persists.

Step 2: Reduce Dose and Frequency
Many patients can taper by:

• lowering the dose
  
  
• taking it every other night
  
  
• reserving it only for severe sleep disruption
  

Step 3: Transition to Evidence-Based Therapies
Use CBT-I resources, behavioral changes, and light therapy when appropriate.

Step 4: Monitor Cardiovascular Status
Especially in patients over 50, those with hypertension, or those developing symptoms:

• new shortness of breath
  
  
• leg swelling
  
  
• fatigue out of proportion
  
  
• nighttime respiratory discomfort
  

Early detection is key.

What the Research Does NOT Prove
To avoid misinterpretation, clinicians must remember:

• It does NOT prove melatonin directly causes heart failure.
  
  
• It does NOT apply to short-term or intermittent melatonin use.
  
  
• It does NOT mean all patients must stop melatonin immediately.
  
  
• It does NOT mean melatonin is dangerous in every context.
  

But it DOES mean:

• We should rethink chronic use.
  
  
• We should monitor cardiovascular risk.
  
  
• We should prioritize safer long-term strategies.
  

Why This Study Is a Turning Point
For years, the medical community lacked high-quality long-term safety data about melatonin.
This new research represents:

• the largest population studied
  
  
• the longest follow-up period
  
  
• the strongest cardiovascular associations to date
  

Even though causation is not proven, the signal is strong enough that clinicians must take it seriously.

We are entering a new era where melatonin can no longer be dismissed as harmless when used daily for years.