Melatonin

Melatonin is a hormone produced primarily by the pineal gland in the brain, with synthesis driven by the suprachiasmatic nucleus in response to environmental light cues. Endogenous melatonin levels rise in the evening as ambient light decreases, peak in the middle of the night, and decline before morning, helping to regulate the timing of the body's circadian sleep-wake cycle.¹ Exogenous melatonin sold as a dietary supplement in the United States is chemically identical to the endogenous hormone but is regulated as a dietary supplement rather than as a drug.¹

Melatonin has been most extensively studied for circadian rhythm disorders, jet lag, and delayed sleep phase syndrome — situations where the timing of the body's sleep-wake cycle is misaligned with the desired sleep schedule. Evidence is generally more supportive of melatonin in these timing-related conditions than for primary insomnia in adults.¹

For general adult insomnia, evidence is more mixed. The 2017 American Academy of Sleep Medicine practice guideline and the 2016 American College of Physicians guideline for chronic insomnia both concluded that there was not enough strong evidence on the effectiveness or safety of melatonin supplementation for chronic insomnia to recommend its routine use, and that cognitive behavioral therapy for insomnia (CBT-I) remains the recommended first-line treatment for chronic insomnia in adults.¹

In children, melatonin has been studied for sleep difficulties associated with autism spectrum disorder, attention-deficit/hyperactivity disorder, and chronic sleep-onset insomnia, with several systematic reviews showing modest improvements in sleep latency and total sleep time in these specific populations.¹ However, long-term safety data in children — including potential effects on hormonal development, puberty, and other developmental outcomes — remain limited, and the NCCIH notes that decisions about melatonin use in children should involve a pediatric clinician.¹

A 2024 NIH report cited by NCCIH found that between 2019 and 2022, approximately 11,000 emergency department visits were associated with unsupervised melatonin ingestion by children 5 years and younger, reflecting both the increase in household availability of melatonin products and the importance of secure storage.¹

Melatonin is most commonly studied at oral doses of 0.5 mg to 5 mg taken approximately 30 minutes to 1 hour before bedtime, though some products are sold at considerably higher doses (10 mg or more) without strong evidence that higher doses produce greater benefit.¹ Some research suggests that lower doses (0.3–1 mg) may be more physiologically appropriate, since they more closely approximate the endogenous nighttime peak, and that higher doses do not consistently outperform lower doses for sleep onset.¹

For jet lag, melatonin is typically taken close to the target bedtime in the destination time zone for the first several days after arrival. For delayed sleep phase syndrome, low-dose melatonin taken several hours before the desired bedtime has been studied for circadian phase advancement, ideally under clinician guidance.¹

Independent product testing has historically shown that the actual melatonin content of commercial products may vary substantially from the label-stated amount, which is one practical consideration when selecting a product.¹

Real-world practice: More is not better with melatonin. The commonly sold 5–10mg doses in the U.S. are pharmacological doses far above what the body produces naturally (0.1–0.3mg). Research suggests that 0.5–1mg is sufficient for most sleep-onset purposes and produces fewer next-day grogginess effects than higher doses. Many users find better results by starting at 0.5mg and only increasing if necessary.

Oral, typically as immediate-release tablets, capsules, gummies, sublingual tablets, or liquid drops. Extended-release formulations are also available.

Standard storage in a cool, dry place out of direct light. Melatonin should be stored securely out of reach of children, given the increase in unintentional pediatric ingestions associated with home availability of gummy products.¹

Short-term melatonin use is generally well-tolerated in adults. Reported side effects include daytime drowsiness, headache, dizziness, and nausea; these are typically mild and self-limited.¹ Melatonin can also cause more vivid dreams or transient mood effects in some users.

Several interactions and considerations are documented:¹

• Anticoagulants and antiplatelets: Melatonin may have mild antiplatelet effects in some studies; caution is reasonable in individuals on warfarin or other anticoagulants
• Blood pressure medications: Melatonin may affect blood pressure, and interactions with antihypertensives have been reported
• Diabetes medications: Melatonin may affect glucose tolerance in some individuals
• Immunosuppressants: Melatonin has immune-modulating properties and may interact with immunosuppressive therapy
• CNS depressants (alcohol, benzodiazepines, opioids, sedating antihistamines): Additive sedation is possible

Pregnancy and lactation: NCCIH notes that there is not enough reliable information about the safety of melatonin during pregnancy or breastfeeding to make confident recommendations, and use during these periods should involve clinician discussion.¹

Melatonin is a hormone, and the long-term effects of nightly supplementation across years — particularly on endogenous melatonin production, hormonal regulation, and other downstream effects — are not fully characterized in the published literature.¹ Short-term use for circadian disruption (jet lag, shift work transition, occasional sleep difficulty) is generally better-supported than chronic nightly use.