Melatonin
Endogenous pineal hormone and MT1/MT2 receptor agonist regulating circadian phase. Low doses (0.1–0.5 mg) shift circadian phase without suppressing next-day cortisol; high doses (5–10 mg, typical US OTC dosing) flood receptors and cause next-day grogginess.
The US OTC market sells 5–10 mg doses that are 10–50× higher than physiological nocturnal peak (~0.1–0.3 ng/mL serum). Research consistently shows 0.1–0.5 mg is sufficient for circadian phase shifting in healthy adults. Higher doses are useful for jet lag acute correction but not for chronic nightly use. Melatonin also has antioxidant properties and may have immune-modulatory effects at pharmacological doses — clinical relevance uncertain.
Chronic high-dose use may downregulate endogenous production (evidence mixed — cycle or use lowest effective dose). Autoimmune conditions: melatonin stimulates immune activity — some protocols avoid it. Drug interactions: anticoagulants (additive with warfarin), immunosuppressants, diabetes medications.
External links to PubMed searches, ClinicalTrials.gov, and FDA materials. We do not host papers — we point at canonical sources.
Dietary supplement (DSHEA) in US. Prescription-only in UK, EU, and Australia — regulatory arbitrage vs US OTC.
Distilled themes from named communities — Reddit threads, forums, creator commentary. Not direct quotes; not clinical evidence. Useful for calibrating expectations against what real self-experimenters report.
Stack convergence point: nearly everyone in longevity/recovery protocols uses some melatonin. Huberman's recommendation of 0.1–0.3 mg has shifted community dosing down from the historical 5–10 mg standard. Many users report better next-day cognition after switching to lower doses.