The Endogenous Melatonin Circadian Curve
Pineal melatonin secretion follows a robust daily rhythm gated by the suprachiasmatic nucleus.
- ~2-4am: Peak time (core body temp minimum nearby)
- ~21:00: DLMO (dim light melatonin onset)
- ~1 pg/mL: Daytime level (near baseline)
- ~50-60 pg/mL: Night peak (plasma concentration)
Endogenous rhythm basics
Placeholder: SCN drives nightly melatonin rise and daytime suppression by light.
Exogenous Dose Timing Relative to the Curve
When a dose is taken relative to DLMO determines its phase-shifting effect.
- 1-10mg: Typical OTC dose (wide commercial range)
- 0.5mg: Effective phase dose (often sufficient)
- ~30-60min: Absorption (time to peak plasma)
- ~45min: Half-life (short duration)
Timing relative to DLMO
Placeholder: earlier dosing before DLMO shifts phase more than late dosing.
Phase Advance Protocol for Delayed Sleep Phase
Low-dose melatonin several hours before target bedtime advances sleep onset.
- 0.5-1mg: Best dose (low-dose chronobiotic)
- 5-7h pre-bed: Timing window (before habitual sleep)
- days-weeks: Onset of effect (gradual entrainment)
- AM bright light: Combine with (reinforces advance)
Advancing a delayed clock
Placeholder: early low-dose melatonin plus morning light advances DSPS.
Phase Shift Strategy for Jet Lag
Melatonin timed to the destination bedtime speeds circadian re-entrainment.
- Advance: Eastward travel (take near dest. bedtime)
- Delay: Westward travel (take later, or skip)
- 0.5-5mg: Typical dose (lower often adequate)
- ~1 day/zone: Re-entrainment (without treatment)
Direction-dependent dosing
Placeholder: dosing direction depends on eastward vs westward travel.
Low-Dose Timing vs High-Dose Sedation
Low doses act as a chronobiotic; high doses mainly sedate without extra phase effect.
- 0.3-1mg: Chronobiotic range (phase-shifting sweet spot)
- >3mg: Sedative range (supraphysiological levels)
- yes: Ceiling effect (more mg ≠ more shift)
- dose-dependent: Next-day grogginess (higher dose, more residual)
Dose-response tradeoff
Placeholder: higher doses trade phase precision for sedation.