The sleep supplement aisle presents melatonin as a universal solution—bottles promising 5mg, 10mg, even 20mg doses line the shelves, each suggesting that more hormone means better sleep. Americans now spend over $1 billion annually on melatonin supplements, with usage tripling over the past decade. Yet the clinical evidence tells a far more nuanced story than the marketing suggests.

Melatonin isn't a sedative. It's a chronobiotic—a hormone that signals timing information to your body rather than inducing unconsciousness. This fundamental misunderstanding shapes how most people use it, often in doses and timing patterns that undermine its actual mechanism of action. The research reveals specific conditions where melatonin demonstrates genuine benefit and others where it performs no better than placebo.

Understanding what the evidence actually supports requires examining different sleep disorders separately, acknowledging dose-response relationships that contradict commercial logic, and confronting quality control problems that make consistent dosing nearly impossible with many products.

Commercial melatonin supplements typically contain doses ranging from 3mg to 10mg, with some products reaching 20mg or higher. This dosing strategy follows intuitive but incorrect assumptions—if some helps, more should help more. The physiological evidence demonstrates precisely the opposite pattern.

Your pineal gland naturally produces approximately 0.1 to 0.3mg of melatonin during nighttime hours. Supplemental doses of 0.5mg to 1mg can elevate blood melatonin to levels 10 to 20 times higher than natural nocturnal peaks. Doses of 3mg or higher push levels into ranges that desensitize melatonin receptors and can paradoxically impair the hormone's sleep-timing effects. Multiple studies have found that 0.3mg to 0.5mg doses produce equivalent or superior effects compared to 3mg doses for sleep onset.

Higher doses also create problems beyond receptor desensitization. Supraphysiological melatonin levels persist longer in the bloodstream, potentially causing morning grogginess and disrupting the normal daytime melatonin suppression that maintains circadian rhythm integrity. The half-life of oral melatonin ranges from 20 to 50 minutes, but massive doses can maintain elevated levels for hours beyond the intended window.

A 2005 MIT meta-analysis examining melatonin dosing found that 0.3mg reduced sleep onset latency as effectively as 3mg, while higher doses showed no additional benefit and increased side effect reports. Yet supplement manufacturers continue escalating doses because consumer psychology equates quantity with potency, and regulatory frameworks don't require efficacy-based dosing for supplements.

Takeaway

Consider starting with the lowest available dose (0.5mg or less, which may require splitting tablets) rather than assuming higher doses work better—physiologically, they often work worse.

Melatonin research quality varies dramatically across different sleep conditions, and conflating these distinct disorders obscures where the hormone genuinely helps. The strongest evidence supports applications involving circadian rhythm disruption rather than general insomnia.

Jet lag represents melatonin's best-supported use case. A Cochrane review examining 10 trials found melatonin significantly reduced jet lag symptoms when traveling across five or more time zones, particularly for eastward travel. Optimal timing involves taking 0.5mg to 5mg at the destination's bedtime for several days after arrival. The evidence here is consistent and mechanistically logical—you're using a timing signal to accelerate adaptation to a new light-dark cycle.

Delayed sleep phase disorder (DSPD)—where the circadian clock runs late, making sleep onset difficult before 2-3am—shows moderate evidence supporting melatonin use. Studies indicate that low-dose melatonin taken 4-6 hours before desired bedtime can advance the circadian phase, though effects are modest and require consistent timing. For primary insomnia without circadian involvement, the evidence weakens considerably. Meta-analyses show melatonin reduces sleep onset latency by approximately 7 minutes on average—statistically significant but clinically marginal for most patients.

Shift work disorder presents mixed results. While theoretically logical, studies show inconsistent benefits, likely because the underlying circadian disruption is ongoing rather than a one-time adjustment. Melatonin cannot override continuous exposure to conflicting light-dark schedules.

Takeaway

Match melatonin use to its actual mechanism: it works best for circadian timing problems (jet lag, delayed sleep phase) rather than general difficulty sleeping, where the average benefit is too small for most people to notice.

Melatonin's classification as a dietary supplement rather than a pharmaceutical means manufacturers face minimal regulatory oversight regarding content accuracy or contamination. This regulatory gap creates significant problems that undermine even evidence-based usage.

A landmark 2017 study published in the Journal of Clinical Sleep Medicine analyzed 31 melatonin supplements from various retailers. The findings revealed that 71% of products tested did not contain melatonin within 10% of their labeled amount. Actual melatonin content ranged from 83% less than labeled to 478% more than labeled. One chewable tablet claiming 1.5mg actually contained 9mg—six times the stated dose.

Perhaps more concerning, the same study detected serotonin contamination in 26% of supplements. Serotonin is a controlled substance in some jurisdictions and can cause adverse effects including serotonin syndrome when combined with certain medications. The contamination likely results from manufacturing processes that inadequately separate melatonin from its synthetic precursors or from cross-contamination in facilities producing multiple supplements.

This variability makes consistent dosing functionally impossible with many commercial products. A person following evidence-based recommendations for 0.5mg might inadvertently take 3mg one night and 0.2mg the next, depending on which tablets they select from the same bottle. Pharmaceutical-grade melatonin products exist in some countries but remain unavailable in markets where supplement classification dominates.

Takeaway

If using melatonin, seek products with third-party verification (USP, NSF, or ConsumerLab certification) to increase the likelihood that actual content matches label claims—though even verification cannot guarantee consistency across all batches.

Melatonin occupies an unusual position—a genuinely bioactive hormone sold as an unregulated supplement, with legitimate applications undermined by inappropriate dosing conventions and quality control failures. The evidence supports specific, limited uses rather than the broad sleep-enhancement claims that drive commercial success.

For jet lag and delayed sleep phase disorder, melatonin offers a reasonable intervention when used at appropriate doses (0.3mg to 1mg) and timing. For general insomnia, the evidence suggests looking elsewhere—cognitive behavioral therapy for insomnia (CBT-I) demonstrates far stronger effects without the quality control uncertainties.

The gap between melatonin's scientific profile and its commercial presentation reflects broader problems in supplement marketing. Effective use requires understanding what the hormone actually does, accepting that more isn't better, and navigating a marketplace where label accuracy cannot be assumed.