Melatonin Supplement

## What it is Melatonin is an endogenous indoleamine hormone synthesized primarily in the pineal gland from tryptophan via serotonin. It was first isolated in 1958 by Aaron Lerner at Yale, who named it for its skin-lightening effect on amphibians. Its central role in mammalian circadian regulation became clear over the following two decades, anchored by Alfred Lewy's work in the 1980s establishing dim-light melatonin onset (DLMO) as the gold-standard biomarker for circadian phase. Endogenous secretion follows a stable circadian pattern: low daytime levels, a sharp evening rise around 2 to 3 hours before habitual sleep onset (the DLMO), peak levels around 3 to 4 a.m., and a gradual morning decline. Peak nighttime levels in healthy adults are roughly 60 to 200 pg/mL. The signal communicates 'biological night' to peripheral tissues and gates sleep onset rather than driving sleep maintenance. Legally, melatonin sits in a regulatory split. The US classifies it as a dietary supplement, available OTC at any dose. The UK, EU, Japan, and Australia regulate it as a prescription medication, typically restricted to 2 mg extended-release for adults over 55 with primary insomnia. The transatlantic split has practical consequences: most US supplement-store melatonin is sold at 3 to 10 mg per dose, while the dose used in European clinical practice is closer to 0.5 to 2 mg. The US dosing convention is roughly 5 to 10 times higher than the dose suggested by the dose-response data, which is the most consistent error users make with this molecule. ## Mechanism of action Melatonin signals through two G-protein-coupled receptors, MT1 and MT2, both expressed densely in the suprachiasmatic nucleus (SCN) of the hypothalamus, which is the central circadian pacemaker. MT1 activation primarily mediates sleep-onset gating; MT2 activation primarily mediates phase-shifting effects. The receptors are also expressed in retina, cardiovascular tissue, gut, and immune cells, accounting for the broader range of physiological effects observed at supraphysiological doses. The pharmacokinetics are short and wide. Oral immediate-release melatonin reaches peak plasma concentrations 30 to 60 minutes after dosing, with a terminal half-life of 30 to 50 minutes. Bioavailability varies enormously between individuals (3% to 76% in published studies) due to first-pass hepatic metabolism via CYP1A2, which is itself induced by smoking and inhibited by fluvoxamine and oral contraceptives. A 5 mg dose can produce plasma levels ranging from physiological to roughly 60-fold above physiological depending on the individual. This pharmacokinetic variability is the hidden reason dose-response data is messy. The same milligram dose produces drastically different exposures across users, which means population-level dose recommendations are blurry approximations. The cleanest approach is to start at the lowest dose that works and titrate up only if needed, rather than starting at a typical-bottle dose of 3 to 10 mg. The inverted-U dose-response curve is real. Brzezinski 2005 (meta-analysis of 17 trials) and Zhdanova 2001 both reported that doses of 0.3 to 1 mg produced peak sleep-onset effects, with higher doses producing equivalent or smaller effects on sleep parameters and substantially more next-day grogginess. The mechanism is plausibly receptor desensitization at sustained supraphysiological exposure. ## Evidence base by outcome ### Sleep onset latency The most robust effect. A 2013 meta-analysis (Ferracioli-Oda) of 19 trials and 1,683 participants reported a mean sleep onset reduction of 7.06 minutes versus placebo. Effect sizes are larger in adults with delayed sleep-wake phase disorder (DSWPD) and in pediatric ASD populations, where reductions of 25 to 60 minutes are reported. In healthy adults without circadian misalignment, the magnitude is modest and most clearly demonstrated at the 0.3 to 1 mg dose range. ### Total sleep time and sleep maintenance Weaker. Meta-analyses report mean increases of 8 to 13 minutes in total sleep time, and the effect is inconsistent across trials. Melatonin gates sleep onset; it does not extend sleep duration in adults whose homeostatic sleep drive is intact. If the chief complaint is sleep maintenance (3 a.m. wake-ups), melatonin is the wrong tool, and extended-release formulations only partially address this. ### Circadian phase shifting and jet lag Melatonin is the most evidence-supported pharmacological intervention for jet lag, particularly eastward travel. A Cochrane review covering 9 RCTs reported reductions in jet-lag severity of roughly 50% at 0.5 to 5 mg taken at the local target bedtime for 2 to 5 days at the destination. The phase-shifting magnitude is roughly 30 to 60 minutes per night when timed correctly. Westward travel responds less well because the natural drift is in the lengthening direction. Shift-work applications follow similar logic and similar effect sizes. ### Pediatric ASD The largest single-population win for melatonin. A Cochrane review covering 12 RCTs in children with ASD and sleep difficulties reported sleep onset reductions of 25 to 50 minutes at 1 to 6 mg taken 30 to 60 minutes before bed. The effect is robust and clinically meaningful, and the safety record over months to years of use is reassuring. ### Pre-surgical anxiolysis A Cochrane review covering 10 RCTs concluded that melatonin produced anxiety reductions comparable to midazolam in pre-operative settings at doses of 3 to 10 mg, with less post-operative cognitive disruption. This is one of the few use cases where higher doses are defensible. ### Antioxidant and other effects In vitro and rodent data show melatonin acts as a direct radical scavenger and modulates immune signaling. The translation to clinically meaningful human outcomes outside sleep is thin. Adjunctive use during chemotherapy and in oxidative stress conditions has small signals across small trials. Treat as exploratory. ### Endogenous secretion at high doses The concern that exogenous melatonin suppresses endogenous production is not well supported by short-term data. Studies of multiple weeks of dosing have not shown sustained suppression of nighttime endogenous secretion. Receptor desensitization at chronic high doses is plausible mechanistically and underdocumented in humans. ## Dosage and protocols The dose-response evidence supports starting at 0.3 to 0.5 mg taken 30 to 60 minutes before target bedtime. This is roughly 1/10th to 1/20th of a typical US supplement bottle. Doses in this range produce peak plasma levels closest to the endogenous nighttime peak. If 0.3 to 0.5 mg is ineffective, a step to 1 to 3 mg is reasonable. Doses above 5 mg are pharmacological rather than physiological and tend to produce next-day grogginess without proportional sleep benefits. Extended-release formulations (Circadin in Europe, ER products in the US) deliver 2 mg over roughly 8 hours and target sleep maintenance in addition to onset. The European prescription label is for adults over 55 with primary insomnia and reflects the population in which the trial evidence is strongest. For jet-lag protocols, 0.5 to 3 mg taken at the local target bedtime for 2 to 5 nights at the destination is the standard approach. For DSWPD or shift-work phase shifting, timing is more important than dose: low doses (0.5 mg) taken 4 to 6 hours before habitual sleep produce larger phase advances than larger doses taken at bedtime. No cycling is required for chronic use, but most users do not need chronic use. Indication-driven dosing (jet lag, occasional poor sleep, shift transitions) makes more sense than nightly indefinite use for most adults, particularly given the modest effect on healthy sleep. ## Side effects and safety The safety record over decades of widespread use is reassuring. Common side effects are mild: vivid dreams, morning grogginess (especially at higher doses), headache, dizziness. Vivid dreaming is dose-dependent and resolves with dose reduction. Morning grogginess at the 0.3 to 1 mg range is rare; at 5 to 10 mg it affects a substantial minority of users. Contraindications are narrow. Autoimmune disease is a theoretical concern given melatonin's immunomodulatory effects, but the human evidence for harm is thin. Concurrent anticoagulant therapy warrants caution because of small reported effects on platelet function. Pregnancy data is insufficient and routine use is not recommended. Drug interactions are mostly metabolic. Fluvoxamine inhibits CYP1A2 and can raise melatonin levels 17-fold; this is a major interaction. Oral contraceptives also inhibit CYP1A2 and can substantially raise plasma melatonin. Smoking induces CYP1A2 and reduces effective dose. Warfarin interaction reports exist but are inconsistent. Benzodiazepines and alcohol produce additive sedation at higher melatonin doses. A 2017 Canadian study analyzed 31 OTC melatonin products and found actual content ranging from 17% below to 478% above the labeled dose, with one in four products containing serotonin contamination. This is the strongest practical case for using a third-party-tested brand: the dose you are taking may not be the dose on the label. ## Stack interactions and timing Melatonin pairs cleanly with magnesium glycinate (NMDA modulation, complementary mechanism), L-theanine (alpha-wave modulation, complementary mechanism), and ashwagandha (HPA axis, complementary mechanism). Pairing with antihistamines, alcohol, or benzodiazepines produces additive sedation and is generally counterproductive: the sedation extends into morning and reduces sleep architecture quality. Timing is more important than dose for most use cases. Taken at bedtime, melatonin acts as a soporific. Taken 4 to 6 hours before habitual sleep, it acts as a phase-advancing agent. Taken in the morning, it can phase-delay (rarely useful). The behavior depends entirely on where in the user's circadian cycle the dose lands relative to the DLMO. Light exposure overrides melatonin signaling. A bright phone screen at bedtime can suppress endogenous melatonin secretion by 50% or more, which means bringing exogenous melatonin into a brightly lit bedroom defeats much of the point. Dim ambient light starting 1 to 2 hours before bed is the highest-leverage habit pairing. ## Practical notes Buy a low-dose product (0.3 to 1 mg) from a brand with third-party testing. The 5 to 10 mg gummy products that dominate the US supplement aisle are not delivering the dose the dose-response data supports, and the contamination risk in untested products is real. ConsumerLab, USP, and NSF certifications are the most reliable third-party signals. Expect onset of effect within 30 to 60 minutes of dosing. If sleep onset is the chief complaint and 0.5 mg taken 30 minutes before bed does not help within 3 to 5 nights, the issue is probably not melatonin-deficiency-shaped and a different intervention is warranted. Storage is straightforward. Keep at room temperature, protected from light. Liquid sublingual forms are degraded faster than tablets and should be used within the labeled window. Most importantly: if you wake up groggy, you took too much. Halve the dose and reassess.