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Evidence Files

Melatonin: The Sleep Hormone That Actually Works — Just Not at the Dose You're Probably Taking

In the United States, melatonin is a cheap OTC supplement sold in 5mg, 10mg, even 20mg doses at every pharmacy and supermarket. In the UK, Germany, and most of the EU, the same molecule requires a prescription — and is only approved at 2mg. The European regulators aren't being overly cautious. They may actually be right.

Verdict

TREATMENT (partially confirmed)

We searched PubMed and Cochrane Library for melatonin evidence. The clinical picture is clearer than most supplements: melatonin has genuine, well-replicated evidence for jet lag and delayed sleep phase disorder. For general insomnia in healthy adults, the effect is real but modest — reducing time to fall asleep by roughly 7–12 minutes on average. The major caveat: most commercial supplements are dosed at 5–20x higher than the doses studied in research, which may reduce effectiveness and cause next-day grogginess.

Why melatonin became Europe's most regulated supplement

Melatonin is not a foreign substance — it's a hormone produced by your pineal gland in response to darkness. Its role is to signal to the body that it's night. This gives it a plausible, well-understood mechanism of action that most supplements lack entirely.

The EU regulatory patchwork reflects genuine uncertainty about dosing, not evidence of ineffectiveness. The UK's Medicines and Healthcare products Regulatory Agency (MHRA) classifies melatonin as a medicine. Germany's BfArM requires a prescription. France makes an exception for food supplements containing up to 1mg — but anything higher requires medical authorisation. The reasoning: at doses above 1–2mg, melatonin acts pharmacologically, not physiologically.

Meanwhile, in the US, the supplement industry sells melatonin in doses that have never been systematically studied for long-term use in healthy adults. A 10mg gummy before bed delivers roughly 50 times the melatonin your body produces naturally at night.

What the evidence actually shows

  • Jet lag — the strongest evidence base. Cochrane systematic review (Herxheimer & Petrie, multiple updates): melatonin taken at the appropriate time significantly reduces jet lag severity when crossing 5+ time zones. Effect is consistent and well-replicated. This is where melatonin earns its reputation
  • Delayed sleep phase disorder (DSPD) — good evidence. Taking low-dose melatonin (0.3–1mg) several hours before the desired sleep time can shift the circadian rhythm forward. Used in clinical practice in European sleep medicine
  • General insomnia in healthy adults — modest evidence. Meta-analyses show melatonin reduces sleep onset latency by approximately 7–12 minutes compared to placebo. Statistically significant, but clinically modest. Not comparable to prescription sleep medications — or to good sleep hygiene
  • The dosing paradox — research by Lewy et al. and replicated elsewhere suggests 0.3mg (physiological dose) is as effective as or more effective than 3mg for circadian phase shifting. Higher doses may blunt the signal. Most US supplements contain 5–10mg
  • Long-term safety — largely unknown. Most trials run 4–13 weeks. Endocrine effects of sustained supraphysiological melatonin doses in healthy adults have not been adequately studied
  • Children and adolescents — some evidence for children with autism spectrum disorder or ADHD-related sleep difficulties. Generally not recommended for healthy children without a clinical indication

What the label claims vs. what research shows

"Promotes deep, restful sleep" (typical 10mg product)

Marketing implies melatonin works like a sleep medication — take it and sleep better. Studies show it primarily helps with sleep timing (when you fall asleep), not sleep depth or quality. At 10mg doses, next-day grogginess is a documented side effect. The clinical trials showing benefit largely used 0.3–2mg.

What research actually supports

Melatonin shifts your circadian clock and modestly speeds sleep onset. It works best when timed correctly relative to your current circadian phase — not just 'taken before bed.' The effective dose is likely 0.3–1mg. For jet lag, timing matters more than dose. For general insomnia, cognitive behavioural therapy (CBT-I) has stronger long-term evidence.

Our Conclusion

Melatonin is one of the more honest supplements on the market — it does what it claims, within limits. For jet lag, the evidence is solid enough that it's worth using. For delayed sleep phase, low-dose melatonin is a legitimate clinical tool. For general insomnia, it offers modest benefit, and probably not at the doses most people are taking. If you're buying melatonin in Europe and can find a 0.5mg or 1mg product, that's closer to what the research supports. If you're taking a 10mg gummy every night and waking up groggy, the dose is the problem — not the molecule.

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This article is for informational purposes only and does not constitute medical advice. Trick or Treatment analyses the presence of clinical studies in open scientific databases — PubMed and Cochrane Library. The absence of studies in these databases does not automatically mean a drug is ineffective, but it does mean its effectiveness has not been confirmed by evidence-based medicine standards. Any treatment decisions should be made together with your doctor.