Quick Facts
- Evidence Level Strong
- Optimal Dose (meta-analysis) 4 mg/day
- Optimal Timing 3 hours before bedtime
- SOL Reduction ~7 min vs placebo
- TST Increase ~8 min vs placebo
- Tolerance None observed
- Strongest Evidence For Jet lag (NNT = 2)
Key Studies
Optimizing the Time and Dose of Melatonin as a Sleep-Promoting Drug
This landmark analysis found that melatonin's sleep benefits peak at 4 mg/day taken 3 hours before bedtime — challenging the conventional recommendation of 2 mg at 30 minutes before bed. Having an insomnia diagnosis and a longer administration-to-sleep interval were significant predictors of benefit. Higher doses showed diminishing returns beyond 4 mg.[1]
Melatonin for the treatment of primary sleep disorders
The foundational melatonin meta-analysis. Sleep onset latency was reduced by 7.06 minutes (95% CI: 4.37–9.75) and total sleep time increased by 8.25 minutes (95% CI: 1.74–14.75). Overall sleep quality also improved significantly. Crucially, effects did not diminish with continued use — no tolerance was observed, which is a key advantage over conventional sleep medications.[2]
Safety of higher doses of melatonin in adults
Evaluated melatonin at doses of 10 mg or higher. Found no increase in serious adverse events and no increase in withdrawals due to side effects. A minor increase in common side effects (drowsiness, headache, dizziness) was observed at a rate ratio of 1.40. The authors concluded melatonin "appears to have a good safety profile" even at high doses.[3]
Melatonin for the prevention and treatment of jet lag
9 of 10 trials found melatonin significantly decreased jet lag when crossing 5+ time zones. The number needed to treat (NNT) was just 2 — meaning for every 2 people who take melatonin for jet lag, 1 benefits significantly. Doses of 0.5–5 mg were effective, with 5 mg producing faster sleep onset. Most effective for eastward travel.[4]
Optimal Dosing & Timing
The 2024 dose-response meta-analysis overturned conventional dosing wisdom. Here's what the research now suggests:
| Dose Range | Evidence | Best For |
|---|---|---|
| 0.5–1 mg | Physiological dose — raises blood levels to normal nighttime range | Circadian re-entrainment, delayed sleep phase |
| 3–5 mg | Most common OTC range; 5 mg produces faster sleep onset than 0.5 mg | Jet lag, general sleep onset |
| 4 mg | Optimal per 2024 meta-analysis for both SOL and TST[1] | Sleep onset insomnia, general use |
| ≥10 mg | Supraphysiological; no additional sleep benefit; more side effects[3] | Not recommended for sleep |
When to Take It
Timing may matter more than dose. The 2024 meta-analysis found that a longer interval between taking melatonin and attempting sleep was a significant predictor of benefit. Their optimal protocol: 4 mg taken 3 hours before desired bedtime — not the conventional 30–60 minutes before bed that most product labels suggest.[1]
For jet lag specifically, the Cochrane review recommends taking melatonin at the target destination bedtime (10pm–midnight), starting the day of arrival. Taking it too early in the day can cause unwanted drowsiness and delay circadian adaptation.[4]
Forms
| Form | Onset | Best For |
|---|---|---|
| Immediate-release | 15–90 min | Sleep onset difficulties |
| Extended-release | Gradual | Sleep maintenance; mimics natural melatonin profile |
| Sublingual | Rapid | Fast sleep onset; bypasses first-pass metabolism |
Evidence by Sleep Condition
| Condition | Evidence | Notes |
|---|---|---|
| Jet lag | Strong (NNT = 2) | Most effective for eastward travel crossing 5+ time zones |
| Sleep onset insomnia | Moderate | SOL reduced ~7 min; more effective with insomnia diagnosis |
| Delayed sleep phase | Moderate | Low dose (0.5–1 mg) 3–5 hrs before desired bedtime |
| Sleep maintenance | Moderate (ER only) | Extended-release formulations; AASM does not recommend for this |
| Shift work disorder | Insufficient | Evidence does not support melatonin for shift work specifically |
How Melatonin Works
Unlike most sleep supplements, melatonin's mechanism is well-characterized:
- Endogenous hormone: Melatonin (5-methoxy-N-acetyltryptamine) is naturally produced by the pineal gland following a circadian rhythm — low during the day, elevated at night. Light exposure suppresses production; darkness triggers it.
- MT1 and MT2 receptors: Melatonin acts on two G protein-coupled receptors. MT1 promotes sleep onset and REM sleep; MT2 is involved in NREM sleep and circadian phase-shifting. Both are expressed in the suprachiasmatic nucleus (SCN), the brain's master clock.
- Thermoregulation: Melatonin binding lowers core body temperature — a key physiological signal for sleep initiation.
- Circadian phase-shifting: Via MT2 receptors, melatonin can reset the internal clock, making it uniquely effective for jet lag and delayed sleep phase.
This well-understood mechanism — acting on the same system as the body's own sleep signal — is part of why melatonin has a favorable safety profile compared to drugs that target GABA receptors (like benzodiazepines).
Safety & Drug Interactions
Melatonin has one of the strongest safety records among sleep interventions. Even at doses of 10 mg+, the 2022 safety meta-analysis of 79 studies (3,861 participants) found no increase in serious adverse events.[3]
Common Side Effects
- Daytime sleepiness (1.66%) — the most common effect, especially with higher doses or late-morning timing
- Headache (0.74%)
- Dizziness (0.74%)
- Vivid dreams — occasionally reported
All side effects are mild and self-limited, resolving quickly after discontinuation. Importantly, no evidence of dependence, withdrawal, or tolerance has been observed — melatonin's effects do not diminish with continued use.[2]
Drug Interactions
| Drug | Interaction | Risk |
|---|---|---|
| Anticoagulants (warfarin) | Possible increased bleeding risk | Moderate |
| Immunosuppressants | Melatonin stimulates immune function; may counteract drug | High |
| Diabetes medications | May lower blood sugar; hypoglycemia risk | Moderate |
| Sedatives / CNS depressants | Additive sedation | Moderate |
| Fluvoxamine (CYP1A2 inhibitor) | Dramatically increases melatonin levels | Moderate–High |
Populations Requiring Caution
- Young children (0–6): Melatonin is the leading cause of unsupervised medication exposure in pediatric emergency departments.[5] Keep out of reach.
- Organ transplant recipients: Immune-stimulating properties could trigger organ rejection.
- Pregnant/breastfeeding: Insufficient safety data.
- People on anticoagulants: Increased bleeding risk; INR monitoring needed.
- Autoimmune conditions: Immune-stimulating properties may exacerbate symptoms.
The Bottom Line
Melatonin has the strongest evidence base of any sleep supplement, supported by multiple large meta-analyses across thousands of participants. The absolute effect sizes are modest — about 7 minutes less to fall asleep and 8 minutes more total sleep — but several factors make it noteworthy:
- It does not cause tolerance, unlike many pharmaceutical sleep aids
- It has an excellent safety profile, even at high doses
- It is remarkably effective for jet lag (NNT = 2)
- The 2024 dose-response meta-analysis suggests most people are dosing suboptimally — 4 mg at 3 hours before bed outperforms the conventional approach
Melatonin is most relevant for people with sleep onset difficulty, circadian misalignment (jet lag, delayed sleep phase), or those seeking a supplement with a well-characterized mechanism and safety profile. It is less effective for sleep maintenance issues, and the evidence does not support its use for shift work sleep disorder.
References
- Cruz-Sanabria F, et al. "Optimizing the Time and Dose of Melatonin as a Sleep-Promoting Drug: A Systematic Review of Randomized Controlled Trials and Dose-Response Meta-Analysis." J Pineal Res. 2024;76(5):e12985. PubMed
- Ferracioli-Oda E, Qawasmi A, Bloch MH. "Meta-analysis: melatonin for the treatment of primary sleep disorders." PLoS One. 2013;8(5):e63773. PubMed
- Menczel Schrire Z, et al. "Safety of higher doses of melatonin in adults: A systematic review and meta-analysis." J Pineal Res. 2022. PubMed
- Herxheimer A, Petrie KJ. "Melatonin for the prevention and treatment of jet lag." Cochrane Database Syst Rev. 2002. PubMed
- Kracht CL, et al. "Melatonin Use in Young Children: A Systematic Review." JAMA Netw Open. 2026. PubMed
- Lim S, et al. "Effects of exogenous melatonin supplementation on health outcomes: An umbrella review of meta-analyses." Pharmacol Res. 2022. PubMed