The Truth About Melatonin

The Truth About Melatonin: What This New Heart Study Reveals

Melatonin has long been seen as the gentle, natural way to fall asleep faster. It’s sold over the counter, it’s cheap, and it’s often described as safe enough to take every night. In fact, I fell into the trap of using it on one of my trips to Durango to get past jet lag (won’t make that mistake again!)…

And it is concerning.  Whenever there is a synthetic ‘easy button’, I get concerned (see Ozempic.  That’s for another day.)

Cheap, artificial, seemingly easy ways to fix long term health issues are always too good to be true.   My concerns were always around ingesting a synthetic version of a hormone your body is supposed to create each day in rhytym with other hormones and stimuli.  We know it dampens the body’s ability to then create melatonin each day naturally (and thus makes sleep harder in the long run), but it also then has a negative knock on effect to your body’s ability to regulate serotonin, cortisol and thyroid stimulating hormones.

BUT, it was such an easy option that millions of people have gotten used to using it every day, as part of their routine.

But a new study presented at the 2025 American Heart Association conference could change that…

The New Study That Got Everyone’s Attention

Researchers at the University of Pittsburgh examined medical records from more than half a million adults with insomnia. They compared those who had used melatonin regularly for at least a year with those who hadn’t used it at all.

The results were surprising. Over five years, the long-term melatonin users had:

• A 90% higher incidence of new heart failure
• 3.5 times higher risk of being hospitalized for heart failure
• Nearly double the overall mortality rate

These findings don’t prove cause and effect, but they raise serious questions. The study authors noted that melatonin use “may not be as harmless as commonly assumed.” And they’re right to be cautious. Most of us assume melatonin is a natural hormone, so it must be safe. But when you take it every night for months or years, it’s not just a sleep aid anymore – it’s a hormone replacement.

What Other Studies Are Starting to Show

This isn’t the first time researchers have raised concerns about melatonin. As more people have started using it every night, we’ve begun to see a pattern of potential issues, particularly with long-term or high-dose use.

1. Increased Risk of Falls and Fractures

A large study in the UK looked at older adults who were prescribed melatonin for sleep. Over the following year, those taking melatonin were 44% more likely to suffer a fracture compared to similar adults who weren’t taking it. The reason? Melatonin can increase nighttime drowsiness and reduce balance, which raises the risk of falls – especially in older people.

2. Next-Day Fog, Dizziness, and Fatigue

Meta-analyses of melatonin trials consistently show mild but noticeable side effects. The most common are daytime drowsiness, headaches, dizziness, and sometimes confusion or “brain fog” the following day. These effects are more likely at higher doses or when melatonin is taken at the wrong time (for instance, too late at night). See the 2022 meta-analysis in Sleep Medicine Reviews for details.

3. Interactions With Blood Pressure and Blood Sugar

Melatonin isn’t inert. It interacts with your body’s regulatory systems – particularly the cardiovascular and endocrine systems. Studies have shown it can:

• Lower blood pressure, which can interfere with medication or cause light-headedness.
• Impair blood sugar regulation in some people, especially those with insulin resistance or diabetes (e.g., a 12% drop in insulin sensitivity in one 3-month trial of 10 mg nightly).
• Slightly increase bleeding risk when combined with blood-thinning drugs, due to melatonin’s mild effects on clotting and platelet function.

If you’re already managing blood pressure or blood sugar, this matters.

4. Hormonal and Developmental Effects

Melatonin is a hormone, and the body’s hormone systems are delicately balanced. In adults, high doses can temporarily suppress certain reproductive hormones. In children, studies show that melatonin appears safe over 1–2 years of use, but data beyond that is limited. Some long-term observational research suggests puberty could be delayed in children who have used melatonin for more than six years continuously. We don’t yet know the full implications of this, but it’s enough to warrant caution.

5. Autoimmune Concerns

Melatonin stimulates parts of the immune system, which can be helpful in some contexts but harmful in others. There are documented cases of melatonin worsening autoimmune conditions like myasthenia gravis and autoimmune hepatitis. This doesn’t mean melatonin causes autoimmunity, but if your immune system is already overactive, adding an immune stimulant could be unhelpful. People with autoimmune conditions should always check with their doctor before taking it. The Mayo Clinic specifically advises against melatonin use for those with autoimmune disease.

The Bigger Picture

Melatonin is not meant to be used long term.  Ideally you don’t use it short term!  But long-term use is not the goal.

As with lots of things – it’s an intervention.  Similar to how you’re not meant to use blood pressure medications for the rest of your life (they’re an intevention so you don’t have a heart attack while you naturally get blood pressure down) – melatonin CAN be used very short term to solve acute sleep issues, while you work on naturally fixing them.

For long-term, nightly use, the science is starting to show cracks in the “completely safe” story.

If you rely on melatonin to sleep, it’s worth stepping back to ask why. Is your sleep disrupted because of stress hormones, blood sugar imbalances, late-night blue light, or inconsistent bedtime habits?

These are the underlying causes that the Alkaline Life approach helps you correct.  We have a whole Sleep Solution Masterclass to address this…quickly and naturally.

The truth is, your body is built to produce melatonin naturally – in perfect amounts, at the right time each night – when your systems are balanced and nourished.

You absolutely should not rely on melatonin as part of your sleep routine.  Similar to takign antacids it not only fails to solve the root cause, it actually makes it harder over time.

Remember – natural is always best.

References

• American Heart Association. Long-Term Melatonin Use Tied to Increased Risk of Heart Failure. Presentation at the AHA Scientific Sessions, Chicago, November 2025. Summary reported by Medscape, November 3, 2025.
• Bregani, E. R., P. Lissoni, and S. Brivio. “Prevention of IL-2-Induced Thrombocytopenia by the Pineal Hormone Melatonin.” Recenti Progressi in Medicina 86, no. 6 (1995): 231–33.
• Edemann-Callesen, H., et al. “Safety of Melatonin in Children and Adolescents: A Systematic Review and Meta-analysis.” EClinicalMedicine 67 (2023): 102136. https://doi.org/10.1016/j.eclinm.2023.102136
• Frisher, M., et al. “Sedative Hypnotics and the Risk of Fracture: A Population-Based Retrospective Cohort Study.” BMJ Open 6, no. 2 (2016): e010303. https://doi.org/10.1136/bmjopen-2015-010303
• Menczel Schrire, O., and M. R. Shapiro. “Adverse Effects of High-Dose Melatonin: A Systematic Review and Meta-analysis.” Sleep Medicine Reviews 63 (2022): 101630. https://doi.org/10.1016/j.smrv.2022.101630
• Nnadi, F., and J. C. Henderson. “Long-Term Melatonin Use and Risk of Heart Failure: Results from a Multicenter Electronic Health Record Study.” Abstract presented at the American Heart Association Scientific Sessions 2025, Chicago.
• Mayo Clinic Staff. “Melatonin: What You Need to Know.” Mayo Clinic, updated August 13, 2025. https://www.mayoclinic.org/drugs-supplements-melatonin/art-20363071