Melatonin timing calculator
Two modes: take it tonight to fall asleep at a target time, or shift your circadian rhythm earlier over several nights. Both use 0.3–0.5 mg — the dose with the best evidence and the fewest side effects.
For occasional sleep-onset help. Low dose mimics the body’s natural evening melatonin rise. Take in dim light — bright light blocks the effect entirely.
- ·Skip alcohol — it blunts the melatonin signal
- ·Avoid screens for 30 minutes after taking
- ·Do not drive within 4 hours
Timing matters more than dose
Melatonin is a circadian signal, not a sedative. It doesn’t knock you out — it tells your body it’s evening. Taken at the right time, this nudges sleep onset and shifts the rhythm. Taken at the wrong time, it can do nothing or push your rhythm in the opposite direction.
The phase response curve for melatonin shows: doses in the evening (about 5 hours before usual sleep onset) advance the rhythm; doses in the early morning (around natural wake time) delay it; doses mid-day do effectively nothing. This is why mistimed melatonin sometimes "stops working" — the user is taking it in the dead zone or, worse, in the delay zone.
Why low-dose is the default here
Most over-the-counter melatonin in the US is sold at 3, 5, or 10 mg per tablet — doses 10–100x higher than the body produces. Higher doses don’t produce more sleep; controlled studies consistently find 0.3–0.5 mg is at least as effective for both sleep onset and phase shifting, with less morning grogginess and fewer reports of vivid dreams.
If you can only find higher-dose tablets, a common trick is to cut a 3 mg tablet into quarters or sixths to approximate 0.5 mg. Liquid forms make exact dosing easier.
The two protocols
Sleep onset aid (occasional)
For nights when you can’t fall asleep: 0.5 mg about 90 minutes before bedtime, in dim light. Avoid screens and bright light for the next half hour. This doesn’t fix chronic insomnia — for that, cognitive behavioral therapy (CBT-I) has stronger evidence than any supplement. But for occasional sleep onset trouble, low-dose melatonin is reasonable.
Phase advance (shifting schedule earlier)
For delayed sleep phase, eastward jet lag, or just wanting to become more of a morning person: 0.5 mg about 5 hours before your target new bedtime. Combine with bright morning light immediately on waking (10–30 minutes outdoors, or a 10,000-lux therapy lamp). Repeat nightly. Expect 30–60 minute advance per night for the first few nights, then diminishing returns.
What melatonin won’t do
Replace sleep hygiene basics (cool room, dark room, consistent schedule, no late caffeine). Fix anxiety-driven insomnia (treat the anxiety). Make you sleep longer if your sleep is being cut short by environment or schedule. Melatonin is a precision tool, not a sledgehammer.
Frequently asked questions
Why 0.5 mg and not the 3 or 5 mg sold in stores?
The 0.3–0.5 mg dose matches physiological evening melatonin levels in the bloodstream. Higher doses (3–10 mg) push blood levels 10–100x above natural — they don’t make you sleep more, but they do increase next-day grogginess, vivid dreams, and headache. Burgess et al (2010) and others have shown the low dose is at least as effective as the high dose for both sleep onset and phase shifting, with fewer side effects.
When should I take melatonin to fall asleep tonight?
About 90 minutes before your target bedtime, in dim light. This mimics the body’s natural evening melatonin rise. Taking it later (right before bed) works less well because the signal hasn’t had time to act.
How does melatonin shift my schedule earlier?
Melatonin acts on circadian receptors in the suprachiasmatic nucleus. Taken 4–6 hours before sleep onset, it triggers a phase advance — your internal clock shifts ~30–60 minutes earlier per night. Combined with bright morning light, this is the most evidence-backed protocol for shifting from a delayed schedule to an earlier one. Used for jet lag (eastward) and delayed sleep phase syndrome.
Is melatonin safe?
Generally yes for short-term use in adults. Side effects are dose-dependent — at 0.5 mg, they’re minimal. Long-term safety data is limited but reassuring; multi-year studies in older adults haven’t shown problems. For children, melatonin should only be used under medical supervision. Drug interactions are real (with sedatives, blood thinners, immunosuppressants) — check with a doctor if you take prescriptions.
Can mistimed melatonin make things worse?
Yes. Taking melatonin in the morning can shift your rhythm the wrong way (phase delay), making it harder to fall asleep at your normal time. The phase response curve has a "dead zone" mid-day and an inverting effect in the early morning. Stick to evening timing.
Should I use melatonin for jet lag?
Yes, for trips across 4+ timezones. Eastward: 0.5 mg ~5 hours before target bedtime in the new timezone, starting 2 days before the flight and continuing 2–3 nights after arrival. Westward: usually not needed — bright evening light works better for delaying your rhythm.