Melatonin and Heart Failure: Should You Be Worried About the Latest Study?

Melatonin is one of the most familiar sleep supplements available, and many people assume that because the body naturally produces melatonin, taking it as a supplement carries little risk.

That assumption came under scrutiny in late 2025 when preliminary research presented at the American Heart Association's Scientific Sessions found an association between long-term melatonin use and a higher rate of heart failure among adults with insomnia.

Headlines quickly raised questions such as: Does melatonin cause heart failure? Is melatonin bad for your heart? Can melatonin cause heart problems?

The findings deserve attention, but they also need context. The research found an association, not proof that melatonin caused heart failure.

Is Melatonin Linked to Heart Failure?

A large observational analysis examined health records from more than 130,000 adults with insomnia. Researchers compared people whose medical records showed long-term melatonin use, defined as at least one year, with similar adults who did not have melatonin use documented.

Over five years, heart failure was diagnosed in approximately 4.6% of people in the melatonin group compared with 2.7% of the matched comparison group.

Researchers also reported higher rates of hospitalization for heart failure and all-cause mortality among those with documented long-term melatonin use.

Those numbers led to headlines suggesting a potential melatonin-heart failure link. However, there is an important limitation: this was an observational study presented as a research abstract.

It does not show that taking melatonin causes heart failure.

Does Melatonin Cause Heart Failure?

Based on the available evidence, we cannot say that melatonin causes heart failure.

Observational studies can identify patterns between groups of people, but they cannot always determine why those patterns exist.

For example, people who regularly use melatonin may differ from people who do not in ways that are difficult to fully capture in medical records. Chronic insomnia itself may also be associated with other health problems.

The researchers attempted to account for many health differences between the two groups, but several limitations remained.

Among them:

• The analysis relied on electronic medical records.
• Over-the-counter melatonin use may not have been completely documented.
• The exact amount of melatonin taken was not consistently available.
• People classified as non-users could potentially have taken over-the-counter melatonin without it appearing in their records.
• Other health or sleep-related factors may have contributed to the differences between the groups.

The study was also presented as a scientific meeting abstract rather than a completed peer-reviewed manuscript, meaning additional research is needed before firm conclusions can be drawn.

Is Melatonin Bad for Your Heart?

The 2025 findings raised a legitimate question about the long-term cardiovascular safety of melatonin, but they do not establish that melatonin is harmful to the heart.

That distinction is important.

Researchers found an association between documented long-term melatonin use and heart failure outcomes in adults with insomnia. They did not demonstrate that melatonin directly damaged the heart or caused those outcomes.

For someone who has been taking melatonin regularly for a long period, particularly someone who already has cardiovascular disease or other medical conditions, the study provides another reason to discuss ongoing supplement use with a healthcare provider.

It is not evidence that everyone who has taken melatonin is at risk of developing heart failure.

What About Short-Term or Occasional Melatonin Use?

The heart failure analysis specifically examined people with documented long-term use of at least one year.

It therefore cannot tell us whether occasional or shorter-term melatonin use has the same association.

Existing health guidance generally describes melatonin as relatively safe for short-term use, while acknowledging that significantly less is known about its long-term safety.

This is one reason it is difficult to apply the 2025 heart failure findings to every person who has ever taken melatonin.

What Are the Known Side Effects of Melatonin?

The possible connection between melatonin and heart failure is still being investigated. By contrast, researchers have documented several more common side effects of melatonin.

Reported short-term side effects include:

• Daytime sleepiness or drowsiness
• Headache
• Dizziness
• Nausea

Less commonly reported effects can include vivid dreams, irritability, stomach discomfort, reduced alertness, or confusion.

Melatonin can also interact with certain medications and may not be appropriate for everyone.

So while heart failure is not currently an established common side effect of melatonin, that does not mean the supplement is completely free of risks or side effects.

Another Issue: Melatonin Supplements May Not Always Match the Label

Melatonin in the United States is sold as a dietary supplement rather than as a prescription medication.

That distinction matters because dietary supplements are regulated differently from prescription and over-the-counter medications.

Research has also found substantial variation in the amount of melatonin contained in some commercially available products compared with what was listed on their labels.

This adds another layer of uncertainty when researchers attempt to study melatonin use over long periods. Two people who report taking the same labeled amount may not necessarily be consuming identical amounts.

Why Long-Term Sleep Problems Deserve Attention Too

The conversation about melatonin and heart health should not obscure another important issue: persistent insomnia itself deserves evaluation.

Difficulty sleeping for a few nights is different from struggling with sleep night after night for months.

Chronic insomnia can have many possible contributors, including:

• Stress and anxiety
• An inconsistent sleep schedule
• Evening screen exposure and blue light
• Sleep apnea
• Restless legs syndrome
• Medication effects
• Pain
• Other medical or sleep disorders

Treating the underlying reason for poor sleep may be more useful than relying indefinitely on a sleep supplement.

For chronic insomnia, treatments such as cognitive behavioral therapy for insomnia (CBT-I) may also be considered as part of a comprehensive sleep evaluation.

Should You Be Worried About Melatonin and Heart Problems?

The latest evidence is better viewed as a reason for continued research rather than proof of a new melatonin side effect.

The 2025 study found a meaningful association between long-term documented melatonin use and heart failure outcomes, but significant unanswered questions remain.

At this point:

• Melatonin has not been proven to cause heart failure.
• The study found an association involving long-term use in adults with insomnia.
• The findings were preliminary and observational.
• Short-term melatonin use cannot be assumed to carry the same risk.
• More research is needed to understand whether there is a true cardiovascular effect.

If you regularly use melatonin and are concerned about melatonin and heart failure, cardiac issues, or other potential side effects, discuss those concerns with your healthcare provider rather than making changes based solely on a headline.

Looking Beyond the Headline

The viral discussion surrounding melatonin illustrates an important lesson in interpreting health research.

A study can uncover a concerning association without proving that one thing caused another.

The heart failure findings should not be dismissed, but they should not be interpreted as evidence that melatonin suddenly became known to cause heart failure either.

For people struggling with persistent sleep problems, the larger question is not simply whether to take a supplement. It is understanding why sleep is difficult in the first place and finding an appropriate long-term approach.

At BASS Medical Group, our sleep medicine specialists can evaluate ongoing sleep problems and help identify possible underlying causes. Schedule an appointment today.

Frequently Asked Questions

Can melatonin cause heart problems?

Current research has not established that melatonin directly causes heart problems. A 2025 observational analysis found an association between long-term documented melatonin use and increased heart failure diagnoses, but it could not prove melatonin caused those outcomes.

Is melatonin linked to heart failure?

One large observational analysis reported a link between long-term documented melatonin use and higher rates of heart failure among adults with insomnia. The findings were preliminary, and additional research is needed.

Is melatonin bad for your heart?

There is currently not enough evidence to conclude that melatonin is inherently bad for the heart. Questions remain about its long-term cardiovascular safety, particularly because long-term use has not been studied as extensively as short-term use.

What are the common side effects of melatonin?

Reported side effects include daytime drowsiness, headache, dizziness, and nausea. Long-term safety is less well understood.