Melatonin (N-acetyl-5-methoxytryptamine) is an endogenous hormone produced by the pineal gland in response to darkness and is the primary biochemical signal regulating the body's circadian rhythm — the internal biological clock that governs sleep-wake cycles, body temperature fluctuations, hormone release, and metabolic processes across a 24-hour period.
In the United States, melatonin is classified as a dietary supplement and is available without a prescription. Despite its widespread use, significant consumer confusion exists regarding appropriate dosage, timing, and indications. Many commercially available melatonin products are formulated at doses substantially higher than those validated in clinical research.
Key distinction: Exogenous melatonin does not function as a sedative — it does not directly induce sleep or produce a hypnotic effect. Rather, it serves as a chronobiotic: it communicates to the body's circadian system that darkness has arrived and facilitates the physiological transition toward sleep.
How Melatonin Works
The synthesis and release of endogenous melatonin begins with darkness-induced suppression of sympathetic input to the pineal gland, leading to the enzymatic conversion of serotonin to melatonin. Serum melatonin concentrations begin rising approximately 2 hours before habitual sleep onset, peak during the middle of the night, and decline in the early morning hours, signaling the transition to the wake phase.
Melatonin exerts its effects by binding to two primary G-protein-coupled receptors: MT1 (associated with sleep promotion) and MT2 (associated with circadian phase-shifting effects). Both receptor subtypes are expressed in the suprachiasmatic nucleus (SCN), the master circadian clock of the brain.
Evidence-Supported Dosage Ranges
General Adult Population
Despite the widespread availability of melatonin products at doses of 5 to 10 mg, the research literature consistently indicates that much lower doses are physiologically effective. A comprehensive review published in the Journal of Biological Rhythms noted that endogenous melatonin levels during peak nighttime secretion are achievable with oral doses as low as 0.1 to 0.5 mg.
| Use Case | Evidence-Supported Range | Timing |
|---|---|---|
| General sleep onset support | 0.5–3 mg | 30–60 min before desired sleep |
| Jet lag (eastward travel) | 0.5–5 mg | Local destination bedtime, 3–5 nights |
| Jet lag (westward travel) | 0.5–3 mg | Local destination bedtime |
| Older adults (55+) | 0.5–2 mg (immediate release) | 1 hour before bedtime |
| Children (physician guidance only) | 0.5–3 mg (age/weight dependent) | As directed by pediatric provider |
The principle of using the lowest effective dose is particularly important with melatonin given its hormonal nature and the potential for receptor desensitization with chronically elevated exogenous administration. Higher doses do not proportionally improve sleep outcomes and may increase the risk of next-day grogginess, headache, and disrupted circadian rhythmicity.
Jet Lag and Circadian Rhythm Adjustment
Melatonin has the most robust clinical evidence base for the management of jet lag disorder. A 2002 Cochrane systematic review concluded that oral melatonin is effective for preventing or reducing jet lag, with consistent benefit across multiple trials. For eastward travel (where the circadian clock must advance), taking melatonin at the local destination bedtime for 3 to 5 consecutive nights following arrival is most effective. Starting melatonin at the destination's target bedtime, rather than the traveler's home-time equivalent, is critical for efficacy.
Older Adults
Melatonin production tends to decline with age, and this age-related reduction in endogenous melatonin is thought to contribute to increased sleep difficulties in older populations. A systematic review published in the British Journal of Clinical Pharmacology recommended melatonin doses of 1 to 2 mg of immediate-release formulation taken 1 hour before bedtime as a first-line approach for sleep difficulties in individuals over 55. Lower starting doses (0.5 to 1 mg) are advisable in older adults due to potentially reduced hepatic clearance.
Children and Adolescents
Melatonin use in pediatric populations should occur exclusively under the supervision and guidance of a licensed pediatric healthcare provider. Long-term safety data for pediatric melatonin supplementation are limited, and its routine use in neurotypical children for sleep concerns is not broadly recommended in current clinical guidelines.
Timing of Administration
The timing of melatonin supplementation is as important as dose selection. Incorrect timing can produce paradoxical effects, shifting the circadian phase in an unintended direction.
- For sleep onset support: Take 30 to 60 minutes before the desired sleep time
- For circadian phase advancement: Take 4 to 6 hours before habitual sleep time
- Avoid light exposure: Blue-spectrum light from screens after taking melatonin will reduce its effectiveness
Safety Profile and Interactions
Melatonin is generally well tolerated at evidence-supported doses. The most commonly reported effects include daytime drowsiness (particularly at doses above 3 mg), headache, and occasional dizziness or nausea.
Clinically relevant interactions include:
- Anticoagulants (warfarin): Potential for enhanced anticoagulant effect
- Immunosuppressants: Melatonin may modulate immune function
- Antidiabetic medications: May affect glucose metabolism; monitor blood glucose
- CNS depressants and benzodiazepines: Additive sedative effects
- CYP1A2 substrates: Fluvoxamine can dramatically elevate plasma melatonin levels
Melatonin use during pregnancy is not recommended in the absence of specific medical indication. Its use during breastfeeding is also not recommended without medical supervision.
Product Quality Considerations
A 2017 study published in the Journal of Sleep Research analyzed 31 commercial melatonin supplements and found that the actual melatonin content varied from 83 percent less to 478 percent more than the labeled dose. Additionally, 26 percent of products contained serotonin as an unintended contaminant.
These findings underscore the importance of selecting melatonin products that have undergone independent third-party analytical testing and certification from organizations such as USP (United States Pharmacopeia), NSF International, or Informed Sport.
Scientific References
- Ferracioli-Oda E, et al. Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PLOS One. 2013;8(5):e63773.
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. 2002;(2):CD001520.
- Brzezinski A. Melatonin in humans. N Engl J Med. 1997;336(3):186-195.
- Vural EMS, et al. Optimal doses for melatonin supplementation therapy in older adults. Drugs Aging. 2014;31(6):441-451.
- Erland LAE, Saxena PK. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content. J Sleep Res. 2017;27(3):e12503.
- Zisapel N. New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation. Br J Pharmacol. 2018;175(16):3190-3199.
This article is provided for informational and educational purposes only and does not represent medical advice or clinical guidance. Melatonin is a hormone; its supplemental use should be approached with care and ideally discussed with a licensed healthcare provider. This content does not constitute a recommendation for the self-management of insomnia, circadian rhythm difficulties, or any other medical condition. The FDA has not approved melatonin supplements for the management of any disease. Melatonin use in pregnant women, nursing mothers, children, and individuals with chronic medical conditions or on prescription medications should occur only under medical supervision. Supplement statements have not been evaluated by the Food and Drug Administration.