Melatonin: Clinical Dose Ranges and What the Research Describes

What melatonin is

Melatonin (N-acetyl-5-methoxytryptamine) is a hormone produced by the pineal gland in response to darkness. It plays a central role in signalling circadian time — it does not cause sleep directly, but its rise in the evening communicates to the body that night has arrived, facilitating the physiological changes that prepare for sleep. Exogenous (supplemental) melatonin can mimic or augment this signal.

Melatonin's regulatory status differs by country. In the United States it is sold freely as a dietary supplement. In the UK and most of Europe it is a prescription-only medicine at doses above 0.5 mg. In Ireland it is a licensed medicine. This regulatory distinction reflects the fact that melatonin is an exogenous hormone, not a vitamin or herbal extract — a distinction that is often obscured in supplement marketing.

For a broader look at melatonin's evidence base across indications, see: What the research says about melatonin.

The clinical dose range

Timing is as important as dose for melatonin's circadian effects. For sleep onset latency, administration 30–60 minutes before the desired sleep time is the typical protocol. For phase-shifting (jet lag, delayed sleep phase), the timing depends on the direction of travel and the intended phase shift.

What trials have measured

The best-established uses of melatonin in clinical trials are jet lag and delayed sleep phase syndrome (DSPS). A Cochrane review of 10 randomised trials found melatonin at 0.5–5 mg significantly reduced jet lag symptoms when taken at the destination bedtime after eastward flights crossing five or more time zones. This is one of the more consistent findings in sleep supplement research.

For general sleep onset latency in adults without circadian disorders, meta-analyses of randomised trials find statistically significant but modest reductions — typically 7–12 minutes on average. This is a real effect but substantially smaller than the claims made in most melatonin marketing.

For shift workers, some trials find benefit for daytime sleep duration and quality, though the evidence base is smaller and more heterogeneous than for jet lag.

Paediatric use has been studied in children with autism spectrum disorder and ADHD, where sleep onset difficulties are common. Some evidence supports benefit in these populations, but the regulatory and safety considerations for melatonin in children differ from adult use and require specific clinical consideration.

Overdosing, not underdosing, is the common product problem

Uniquely among the ingredients in this database, the primary commercial dosing problem with melatonin is systematic overdosing rather than underdosing:

• 5–10 mg as standard: Many commercial products position 5–10 mg as a standard adult dose. Trial evidence does not support this relative to lower doses for most individuals.
• Labelling inaccuracy: A widely cited 2017 analysis of 31 melatonin supplements found that actual melatonin content varied from 83% below to 478% above the labelled dose. Products claiming 1 mg were found to contain as much as 5.7 mg.
• Morning grogginess risk: At higher doses, melatonin's sedative effects may persist into the morning, impairing alertness and potentially affecting driving safety.

Documented safety considerations

Short-term melatonin use in healthy adults at doses within the trial range has a well-established safety record in terms of serious adverse events. However, several considerations are documented: daytime drowsiness and impaired alertness when used at high doses or poorly timed; potential interactions with anticoagulants, antidiabetic medication, and immunosuppressants; and uncertain effects on reproductive hormone levels with long-term use. The safety of long-term habitual melatonin use in healthy adults is less well characterised than short-term use.

As noted above, the regulatory status in the UK and Europe means that obtaining melatonin at therapeutic doses legally requires a prescription — informal importation of US-formulated supplements carries legal and quality risks in these markets.

How Proco Scanner evaluates it

When the Scanner reads a melatonin product, it checks the declared dose against the 0.3–5 mg evidence-based range and flags products above 5 mg as exceeding trial doses for most indications. Products with undisclosed timing guidance are also noted, as timing context is integral to melatonin's evidence base.

Proco Scanner reads any supplement label and surfaces what the published research describes for each ingredient — dose, evidence quality, and known considerations. Coming to iOS. Join the waitlist for early access.