Melatonin Dosage Calculator

Melatonin is the most commonly self-prescribed sleep aid in the United States — and one of the most consistently misused. Drugstore products typically deliver 3, 5, or even 10 milligrams, while every controlled trial measuring effects on sleep onset and circadian timing shows that 0.3–0.5 mg matches or beats the higher doses with fewer side effects. Melatonin is a chronobiotic — a circadian timing signal — not a sedative. Treat it as a hormone, not a sleeping pill.

Enter your age, body weight, the goal (sleep-onset insomnia, jet lag, shift work, or DSWPD), and your current sleep window. The tool returns: the recommended dose in milligrams, the optimal time to take it (relative to your dim-light melatonin onset, or DLMO), the expected onset of effect, and the half-life-adjusted clearance time so you don't carry residual melatonin into morning.

Melatonin is rapidly absorbed and reaches peak plasma concentration in 20–60 minutes. Its elimination half-life is short — 20–50 minutes for immediate-release formulations — but supraphysiological doses produce blood levels well above natural endogenous overnight levels for 6–10 hours, which is why 5 mg pills can cause vivid dreams, morning fog, and next-day mood effects.

The melatonin phase response curve (PRC) describes how the same dose shifts your circadian clock differently depending on when you take it. Doses given in the late afternoon to early evening (roughly 5–7 hours before habitual sleep) phase-advance the clock — pulling sleep onset earlier. Doses given in the early morning phase-delay it. This is the mechanistic basis for using melatonin to treat DSWPD and jet lag.

1. Eastward travel (advance clock): take 0.5 mg at the new local bedtime for 3–5 nights, paired with morning bright light at destination.
2. Westward travel (delay clock): take 0.3 mg only if you wake during the second half of the night; combine with evening light exposure.
3. ≥6 time zones: start the protocol 1–2 days before departure.
4. Avoid alcohol and unnecessary caffeine for the first 48 hours after arrival — both fragment recovery sleep.

• Headache, dizziness, vivid dreams, and daytime sleepiness — usually dose-dependent.
• Reduced morning alertness with doses ≥3 mg, especially in older adults.
• Drug interactions: warfarin, immunosuppressants, anticonvulsants, and some antidepressants.
• Independent product testing (ConsumerLab, JAMA 2017) found melatonin content in commercial products varying from 17% to 478% of the labeled dose — buy USP-verified or pharmaceutical-grade only.

• AASM Clinical Practice Guideline: Pharmacologic treatment of chronic insomnia (2017).
• Auger et al., Clinical Practice Guideline for the Treatment of Intrinsic Circadian Rhythm Sleep-Wake Disorders, J Clin Sleep Med (2015).
• Zhdanova et al., Melatonin treatment for age-related insomnia, J Clin Endocrinol Metab (2001).
• Erland & Saxena, Melatonin natural health products and supplements: presence of serotonin and significant variability in melatonin content, J Clin Sleep Med (2017).