Melatonin — EU research guide.

What is Melatonin?

Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine hormone made mainly by the pineal gland at night. It is thought to act on melatonin receptors (MT1 and MT2) and to signal night-time to the body clock; this receptor mechanism is general pharmacology and was not re-checked against a source for this guide. It is studied for insomnia, jet lag and other circadian rhythm problems, and its sleep effect is modest and tied to timing relative to the body clock. It is not a peptide.

What does the research show?

A meta-analysis of 19 randomised placebo-controlled trials (1,683 people with primary sleep disorders) found that melatonin shortened sleep-onset latency by 7.06 minutes (p<0.001) and increased total sleep time by 8.25 minutes (p=0.013), with a small improvement in sleep quality (SMD 0.22); the effect is statistically significant but modest (Ferracioli-Oda 2013). A Cochrane review of 10 jet-lag trials (9 of adequate quality) found that 8 reported less jet lag after flights across five or more time zones, with an estimated number needed to treat of 2 (Herxheimer and Petrie 2002; a 2008 update search found no new trials). In a 6-month randomised trial of the licensed prolonged-release product Circadin in older adults with insomnia, sleep latency was about 19 minutes shorter than with placebo after 3 weeks, with no tolerance seen and adverse-event rates similar to placebo (Wade 2010). A review of 50 controlled trials found adverse events generally minor and short-lived (Foley and Steel 2019), although the Cochrane review noted case reports of possible harm in people with epilepsy or taking warfarin. All of this concerns oral products; no controlled human trials of an injectable vendor vial were identified.

EU legal status

Melatonin is an authorised medicine in the EU as Circadin 2 mg prolonged-release tablets (centralised procedure, marketing authorisation of 29 June 2007, holder RAD Neurim Pharmaceuticals EEC SARL) for short-term treatment of primary insomnia with poor sleep quality in patients aged 55 or over. Other melatonin products are regulated nationally: in several member states lower-strength products are sold as food supplements under national limits, and two EU health claims (jet lag; time to fall asleep) exist under Regulation (EU) 432/2012 according to a secondary source, but the status differs per country and must be checked locally. An injectable vial from a research vendor is not an authorised EU medicine; no authorised injectable melatonin was found, although this negative was not exhaustively verified. Melatonin is not named on the 2026 WADA Prohibited List, as read from a national anti-doping agency copy (the WADA original was not readable).