Research dossier
Clinical research on Melatonin
8 trials reviewed across 1 indication.
Strongest evidence
Sleep onset and circadian alignment
Mechanism
Melatonin binds MT1 and MT2 receptors in the suprachiasmatic nucleus, signaling the brain's master clock that biological night has begun. The effect is chronobiotic — it shifts and reinforces circadian timing — not sedative-hypnotic.
The honest dosing story: 0.3–1 mg taken 30–60 minutes before bed is as effective as 5 or 10 mg for sleep onset, and avoids the next-day grogginess and cortisol disruption that comes with mega-doses. Strongest indications are jet lag, delayed sleep-phase disorder, shift-work transitions, and pediatric autism-related insomnia.
Most useful for circadian-misalignment problems (jet lag, shift work, DSWPD). Less useful for sleep-maintenance insomnia and night-time anxiety. Healthy young adults with normal circadian rhythms typically gain very little.
Trials cited
Cochrane review — melatonin for jet lag
positive · Systematic review
Herxheimer & Petrie, 2002, Cochrane Database of Systematic ReviewsCochrane review of 10 randomized trials concluded melatonin taken close to local bedtime at the destination is remarkably effective at reducing jet lag after flights crossing five or more time zones, with strongest effect for eastward travel. The clearest indication for melatonin in the entire literature.
Doses between 0.5 and 5 mg performed similarly. Larger doses were not more effective — they just produced more next-day grogginess.
Zhdanova — melatonin dose-response in older adults
positive · RCT
Zhdanova et al., 2001, Journal of Clinical Endocrinology & Metabolismn=300.3 mg — a physiologic dose — restored sleep efficiency in poor sleepers and brought plasma melatonin into the normal nighttime range. The 3.0 mg dose also worked but produced hypothermia and pushed melatonin into morning hours, dragging next-day cortisol. Normal sleepers saw no benefit at any dose.
Small (n=30) but the cleanest dose-response trial in the literature. The retail-gummy dose of 5–10 mg has no advantage over 0.3 mg and several disadvantages.
Ferracioli-Oda — melatonin for primary sleep disorders meta-analysis
positive · Meta-analysis
Ferracioli-Oda, Qawasmi, Bloch, 2013, PLoS ONEn=1683Pooled 19 RCTs, 1,683 subjects. Melatonin reduced sleep onset latency by 7.06 minutes, increased total sleep time by 8.25 minutes, and modestly improved sleep-quality scores (SMD 0.22). Real but modest — comparable to a strong cup of decaf, not to z-drugs.
Effects are statistically reliable and clinically modest. People expecting transformative sleep effects from melatonin are usually disappointed.
Auld — primary sleep disorders systematic review
positive · Systematic review
Auld, Maschauer, Morrison, Skene, Riha, 2017, Sleep Medicine ReviewsSystematic review of 12 RCTs from 5,030 screened citations. Strongest evidence for reducing sleep onset latency in primary insomnia and for entraining circadian rhythm in delayed sleep-phase syndrome and blind individuals. Modest evidence elsewhere.
Heterogeneity of doses, formulations, and timing makes effect-size pooling imperfect. Authors call for larger trials with consistent protocols.
van Geijlswijk — melatonin for delayed sleep-phase disorder
positive · Meta-analysis
van Geijlswijk, Korzilius, Smits, 2010, SleepPooled meta-analysis confirmed melatonin advances sleep-wake rhythm in delayed sleep-phase disorder — moving the biological night earlier. Effect on sleep onset is consistent. The biggest variable is timing: take it 4–6 hours before current sleep onset, not at bedtime.
Timing matters more than dose. Taking melatonin at the wrong circadian phase can shift the rhythm in the wrong direction.
Wade — prolonged-release melatonin (Circadin) in older insomnia
positive · RCT
Wade et al., 2007, Current Medical Research and Opinionn=354Industry-fundedOlder adults with primary insomnia on Circadin 2 mg showed significant improvements in self-rated sleep quality and next-morning alertness versus placebo over 3 weeks. The prolonged-release form is the basis for the EU prescription melatonin product approved for short-term insomnia in adults over 55.
Older population only — the data does not extrapolate to younger adults. Manufacturer-funded.
Xiong — melatonin for sleep in children with autism
positive · Meta-analysis
Xiong et al., 2023, NeuropediatricsMeta-analysis confirmed shorter sleep onset latency, longer total sleep time, and fewer night wakings in children with ASD on melatonin. The evidence base in pediatric ASD insomnia is among the strongest pediatric melatonin indications.
Pediatric long-term safety data is limited. Effects on puberty timing remain incompletely studied. Clinician supervision recommended for chronic pediatric use.
Honest-evidence ledger — 1 trial that didn’t move the needle
Surfacing failed trials alongside the positive evidence. Leaving them out would be marketing, not science.
Pediatric melatonin overdose surge
negative · Observational
Lelak et al., 2022, MMWR Morbidity and Mortality Weekly Report (CDC)n=260435CDC surveillance of US poison-control calls counted 260,435 pediatric melatonin ingestions between 2012 and 2021 — a 530% rise across the decade, with hospitalizations and deaths concentrated in unsupervised settings. Gummy formulations marketed like candy are the dominant driver.
Not an efficacy trial — included as essential context. Retail melatonin is not a benign substance for kids in unrestricted access settings.
2 forms of Melatonin compared
Standard immediate-release melatonin
Variable — oral bioavailability ranges 1–37%; sublingual is faster
Best forSleep onset, jet lag, circadian shifting0.3–1 mg taken 30–60 minutes before target bedtime is the sweet spot. The Zhdanova 2001 dose-response trial is the cleanest evidence: 0.3 mg restored sleep efficiency in older poor sleepers; 3 mg did not work better and produced morning grogginess.
sleep0.3–1 mgCircadin (EU prescription, 2 mg)
Prolonged-release melatonin
Designed to mimic endogenous overnight melatonin curve
Best forSleep maintenance and quality in adults over 55 with primary insomniaTwo-mg Circadin tablets release across the night rather than as a bolus. The Wade 2007 RCT supports use in older adults; available by prescription in the EU and OTC in the US under various brands. Better choice than immediate-release if you wake at 2–3 AM.
sleep2–2 mg
Side effects and drug interactions
Side effects
Next-morning grogginess
Common · Common above 3 mg, rare below 1 mg
The most common side effect at retail doses. Driven by melatonin still circulating into morning hours, suppressing cortisol awakening response. Disappears at 0.3–1 mg doses.
Vivid dreams or nightmares
Uncommon
Some users report unusually vivid or disturbing dreams, more pronounced at higher doses.
Headache
Uncommon
Mild headache occurs in roughly 5% of trial participants, typically resolving with dose reduction.
Daytime sleepiness
Common
Strongly dose-dependent. At retail doses (5–10 mg), residual sleepiness through the morning is common.
Impaired glucose tolerance
Uncommon · Documented at 5 mg; effect worsens when dosed near meals
Melatonin acutely blunts insulin secretion via MT2 receptors on pancreatic beta cells, raising post-meal glucose. The effect is largest when the dose overlaps with eating — a morning dose, or eating close to a nighttime dose, produces a markedly larger glucose spike than an evening dose on an empty stomach. Most relevant for people with prediabetes, diabetes, or the common MTNR1B risk variant. Practical takeaway: take melatonin at night, away from food.
Hormonal effects
Rare
Melatonin is a hormone. Long-term high-dose use may interact with reproductive hormone signaling. Pediatric long-term safety, particularly around puberty, is not fully established.
Pediatric overdose risk
Severe
US poison-control calls for pediatric melatonin ingestion rose 530% between 2012 and 2021. Gummy formulations marketed as candy are the dominant driver. Hospitalizations and deaths have occurred in unsupervised settings.
Drug interactions
Additive effect
benzodiazepinesz-drugs (zolpidem, eszopiclone)sedating antihistaminesalcoholAdditive sedation. Stacking melatonin with other CNS depressants amplifies daytime impairment.
Combine only with clinician input. Do not drive if combining.
Additive effect
warfarinanticoagulantsCase reports describe altered INR on melatonin. The mechanism is not fully resolved.
If you take warfarin, consult your prescriber and monitor INR closely after starting.
Reduces nutrient status
fluvoxamineciprofloxacinestrogensThese drugs inhibit CYP1A2, the enzyme that clears melatonin. The result is much higher and longer-lasting melatonin levels — and stronger next-day sedation.
Use lower melatonin doses if combining, or skip melatonin while on these medications.
Other
immunosuppressantscalcineurin inhibitorsMelatonin has mild immunostimulatory effects.
Avoid in transplant recipients and active autoimmune disease without specialist input.
Other
antihypertensivesbeta-blockersBeta-blockers suppress endogenous melatonin and can create a deficiency state. Melatonin supplementation may help sleep on beta-blockers but can interact with blood-pressure control.
Discuss with your prescriber if you are on beta-blockers and have new-onset insomnia.
Other critical caveats
- Take 0.3–1 mg, not 10 mg. The Zhdanova 2001 dose-response data is unambiguous — bigger does not work better, it just lingers and disrupts your morning. Most retail gummies are 5–10x the effective dose.
- Never take melatonin during the day. Daytime dosing shifts circadian rhythm in the wrong direction and produces next-day grogginess, not better sleep.
- Do not give melatonin to children casually. Pediatric overdose calls are up 530% since 2012. Use only for diagnosed sleep disorders, with clinician input, and store as you would a medication — not on the kitchen counter.
- If you take warfarin, immunosuppressants, fluvoxamine, or estrogens, talk to your prescriber before starting. Pharmacokinetic interactions can produce unexpectedly high melatonin levels.
- Melatonin is a circadian timing tool, not a sedative. If you have sleep-maintenance insomnia (waking at 3 AM), a prolonged-release formulation or a different intervention is more likely to help than a standard melatonin gummy.
Frequently asked
How much melatonin should I take?
0.3–1 mg, taken 30–60 minutes before target bedtime. The Zhdanova 2001 dose-response trial showed 0.3 mg restored sleep efficiency in older poor sleepers, and 3 mg did not work better — it just produced hypothermia and morning grogginess. Most US retail products contain 3, 5, or 10 mg, which is 5–30x the effective dose. Buy a 1 mg product or split a 3 mg tablet.Why are gummies usually 5 or 10 mg if 0.3 mg is effective?
Marketing. Bigger numbers signal stronger to consumers; the supplement industry exploits this. The clinical literature is clear that 0.3–1 mg matches or beats higher doses for sleep onset, with fewer side effects. Independent assays have also shown actual melatonin content often ranges from roughly 80% below to nearly 5x above the label, and one analysis of 31 products found about a quarter were also contaminated with serotonin — another reason precise dosing is harder than it looks, and USP-verified products are worth seeking out.Will melatonin help my insomnia?
It depends on what kind. Melatonin is a circadian timing signal, not a sedative-hypnotic. It works well for jet lag, shift-work transitions, delayed sleep-phase disorder (people who can't fall asleep until 3 AM), and some pediatric autism sleep problems. It works modestly for general primary insomnia — Cochrane-pooled effect is about 7 minutes of sleep-onset reduction. It does not work well for stress-driven middle-of-the-night waking.Is melatonin safe long-term?
For adults, short-term safety (up to a few months) is well-established at standard doses. Long-term safety (years) has not been studied rigorously. For children, the picture is murkier — pediatric chronic use, particularly through puberty, has unknown effects on hormone development. Default to the lowest effective dose, the shortest needed duration, and clinician oversight for pediatric chronic use.Is melatonin addictive?
No, in the chemical-dependence sense — there is no withdrawal syndrome, no dose escalation pattern, no compulsive use. Concerns about 'dependency' are usually psychological habituation: people feel they cannot sleep without it. Melatonin does not suppress endogenous production at standard doses, and stopping does not produce rebound insomnia.Can I take melatonin every night?
You can, but for most use cases you do not need to. For jet lag, take it for 3–5 nights at the destination. For DSWPD, use it as a circadian-shifting tool while you also fix sleep timing behaviorally. Nightly indefinite use is reasonable in older adults with primary insomnia at low dose, but is not necessary for most healthy adults.What is Circadin and is it different?
Circadin is a 2 mg prolonged-release melatonin tablet, prescription-only in the EU, OTC in the US under different names. It releases melatonin slowly across the night rather than as a bolus, mimicking the endogenous overnight curve. Better choice than immediate-release if you wake at 2–3 AM and cannot fall back asleep.
References
- 01NCCIH — Melatonin: What You Need To Know
- 02AASM Clinical Practice Guideline — Pharmacologic Treatment of Chronic Insomnia
- 03Erland & Saxena 2017 — Melatonin supplements: serotonin contamination and label variability (J Clin Sleep Med)
Last reviewed2026-05-07