Melatonin Dose & Timing Calculator

Sleep-onset insomnia. 0.3–3 mg IR, 30–60 min before bed. Ferracioli-Oda 2013 (PMID 23691095, 19 RCTs n=1683) reported a 7.06-min sleep-latency reduction and 8.25-min increase in total sleep time at modest doses. The dose-response paradox is the wedge: 0.3 mg matches 5 mg in head-to-head trials, with fewer next-morning side effects. The calculator starts low and only escalates with non-response.

Eastward jet lag. 0.5–5 mg IR at destination bedtime, day of arrival, continuing 3–5 nights. Herxheimer & Petrie 2002 Cochrane (PMID 12076414, 9 of 10 trials positive, NNT=2) confirmed efficacy for ≥5 time zones eastward; westward and short trips do not consistently benefit. Crucially: timing matters — wrong-time dosing delays adaptation. PR is relatively ineffective for jet lag (Cochrane explicitly noted 2 mg slow-release underperformed IR), so the calculator flags PR override as form-mismatch.

Delayed sleep phase syndrome (DSPS). 0.5–3 mg IR, 4–6 hours BEFORE desired bedtime. Mundey 2005 (PMID 16295212) demonstrated phase advance is timing-dependent — 5 mg at 6 PM advanced sleep onset by 82 minutes; the same dose at bedtime produced no phase advance. Combine with morning bright-light exposure (10,000 lux × 30 min on waking). Expect 60–90 min phase advance after 4–8 weeks of consistent timing.

Age-related insomnia (55+). 2 mg PR (Circadin formulation), 60–120 min before bed. Lemoine 2007 (PMID 18036082, n=170) showed 19% improvement in sleep quality and morning alertness, no withdrawal effects, no rebound insomnia. Wade 2010 (n=791) confirmed sustained benefit at 6 months without tolerance. Endogenous production declines 30–50% with age; PR mimics the natural overnight secretion curve more closely than IR. Reassess fall risk — morning grogginess plus baseline gait instability is the dominant adverse-event profile in this group.

CYP1A2-aware floor. Slow CYP1A2 metabolizers (CYP1A2*1F homozygotes, oral contraceptive users, fluvoxamine co-administration) get 2–3× higher exposure from any given dose. Braam 2010 (PMID 20576063) documented loss-of-response in slow metabolizers — counterintuitively, lower doses restored efficacy by allowing residual melatonin to clear between nights. The calculator floors slow metabolizers at 0.3 mg with a 1 mg ceiling.

T2DM safety signal. Lauritzen 2022 (PMID 35619221, n=17, 10 mg × 3 months crossover) reported a 12% reduction in insulin sensitivity in T2DM patients. The 63-RCT cardiometabolic MA found no aggregate effect on HOMA-IR or HbA1c, suggesting the signal is dose- and population-specific (MTNR1B rs10830963 G allele likely involved). The calculator does not refuse; it surfaces the flag and recommends fasting-glucose monitoring at baseline and every 3 months. Lower doses (0.3–1 mg) are less likely to provoke the effect.

Cross-cutting safety priorities. Pregnancy and lactation are absolute contraindications (crosses placenta and breast milk). Major interactions: fluvoxamine (12–17× exposure), warfarin (potentiated anticoagulation, INR monitoring), oral contraceptives (2–3× exposure), CNS depressants (additive sedation). Product quality is the single biggest real-world risk — Erland 2017 (PMID 27855744) found −83% to +478% label accuracy across 31 retail products and 26% contained undisclosed serotonin. Buy USP-verified or NSF-certified.