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 for most supplements. For jet lag, Cochrane found nine of ten trials positive with a number needed to treat of 2. For general insomnia in healthy adults, a meta-analysis of 19 studies found a real but modest effect: 7 minutes faster to fall asleep and 8 minutes more total sleep. The main caveat concerns dose: the jet lag trials found 0.5–5 mg similarly effective and nothing gained above 5 mg — while retail gummies of 10 mg and more are common.
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 — and, unusually, trial results that bear the mechanism out: strongly for jet lag, modestly for insomnia.
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 is double the dose above which Cochrane's jet lag trials found no additional benefit.
What the evidence actually shows
Melatonin is unusual in this section: the evidence is good, and reading it closely makes it more useful rather than less.
- Jet lag is where melatonin genuinely earns its reputation. The Cochrane review found nine of ten trials showed reduced jet lag when melatonin was taken close to target bedtime after crossing five or more time zones, with a number needed to treat of 2 — an unusually strong figure. The reviewers call it "remarkably effective" and recommend it to adult travellers crossing five or more zones
- Timing matters more than dose, and getting it wrong backfires. The same review notes that doses between 0.5 and 5 mg work similarly, that above 5 mg adds nothing, and that taking it at the wrong time of day causes sleepiness and delays adaptation. This is the detail most packaging omits entirely
- For general insomnia, the effect is real and small — here are the actual minutes. A meta-analysis of 19 studies in 1,683 people found melatonin cut time to fall asleep by 7.06 minutes and increased total sleep time by 8.25 minutes. Sleep quality improved with a standardised effect of 0.22
- Those effects don't fade with continued use. The same authors note the benefit does not appear to dissipate over time — a genuine advantage over sleeping pills, and the reason they conclude melatonin may have a role despite a smaller absolute benefit than prescription hypnotics
- Long-term safety is largely unstudied. Most trials run weeks, not years. The endocrine effects of sustained supraphysiological doses in healthy adults have not been adequately characterised — which is the actual reason for European caution, not doubts about efficacy
- Children and adolescents — some evidence in children with autism spectrum disorder or ADHD-related sleep difficulties. 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 deeply. For insomnia, the pooled trials show a modest effect: 7 minutes faster to sleep, 8 minutes more of it. And more is not better: in the jet lag trials, nothing was gained above 5 mg.
What research actually supports
Melatonin works best as a timing signal. For jet lag, Cochrane found it remarkably effective when taken near target bedtime at the destination — and counterproductive when taken at the wrong time of day. Doses of 0.5–5 mg were similarly effective. For chronic insomnia, cognitive behavioural therapy has stronger long-term evidence.
Frequently asked questions
+How much faster will melatonin get me to sleep?
About seven minutes. A meta-analysis of 19 studies in 1,683 people found melatonin reduced time to fall asleep by 7.06 minutes and increased total sleep time by 8.25 minutes versus placebo. Those are real, statistically solid numbers — and worth picturing concretely before expecting a sleeping pill.
+Does melatonin work for jet lag?
This is its strongest indication by a distance. Cochrane's review found nine of ten trials showed benefit after crossing five or more time zones, with a number needed to treat of 2 — meaning roughly one in two travellers benefits. The reviewers describe it as remarkably effective and recommend it specifically for eastward flights across five or more zones.
+When should I take it?
Timing is the part that actually matters, and it's the part labels leave out. For jet lag, Cochrane's trials used doses taken close to target bedtime at the destination, roughly 10pm to midnight local time. Taken at the wrong time — early in the day — melatonin causes sleepiness and delays your adaptation, making the problem worse rather than better.
+Is a 10 mg dose better than 1 mg?
No, and this is where the US and EU markets diverge. The jet lag review found doses between 0.5 and 5 mg similarly effective, with nothing gained above 5 mg. A 10 mg gummy is not a stronger version of a working dose; it's a dose past the point where more stops helping, with next-day grogginess as the likely result.
+Is it safe to take every night indefinitely?
Nobody really knows, and that uncertainty — not doubt about whether it works — is why most of Europe treats it as a medicine. Most trials run weeks rather than years, and the endocrine effects of sustained high doses in healthy adults haven't been properly studied. For chronic insomnia specifically, cognitive behavioural therapy has considerably stronger long-term evidence than any pill.
Our Conclusion
Melatonin is one of the more honest products in this section — it does what it claims, within limits worth knowing precisely. For jet lag the evidence is genuinely strong: nine of ten trials positive, a number needed to treat of 2, and a Cochrane review willing to use the word "remarkably". For general insomnia the effect is real and small — seven minutes faster to sleep, eight minutes more of it — with the notable advantage that it doesn't fade with continued use. Two practical points follow. Timing beats dose: taken at the wrong hour it delays adaptation rather than helping, and nothing above 5 mg adds anything. And if you're taking a 10 mg gummy nightly and waking up groggy, the dose is the problem, not the molecule. For chronic insomnia, the intervention with the strongest long-term evidence isn't a supplement at all — it's cognitive behavioural therapy.
Sources
Every claim in this article rests on a primary publication. Links go to the publisher's site or to PubMed, the US National Library of Medicine database.
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.