Melatonin Timing Calculator
Most people take melatonin at the wrong time and at the wrong dose. Melatonin works as a timing signal, not a sedative, and its effectiveness depends almost entirely on when it's taken relative to your internal clock, not how much you take.
The DLMO principle
Your body begins producing melatonin at a specific moment each evening called the Dim-Light Melatonin Onset (DLMO). This occurs roughly 2 hours before you naturally fall asleep and serves as the circadian system's "lights out" signal. Taking melatonin supplements timed to coincide with or precede this window, rather than at bedtime, when DLMO has already passed, is the key insight from 30 years of Lewy et al. research.
The phase response curve for melatonin works as follows: supplements taken before DLMO advance the clock (shift it earlier); supplements taken after DLMO have little effect or may slightly delay it. This is why taking melatonin at 11pm to fall asleep at 11pm is essentially useless for any purpose beyond mild sedation.
The dose problem
The typical supermarket melatonin product contains 5–10mg. The dose required for circadian phase shifting is approximately 0.5mg, one-tenth to one-twentieth of what's commonly sold. The reason for this disconnect is partly commercial and partly regulatory: in the US, melatonin is sold as a supplement, not a drug, so dose labelling is unregulated. In the UK and most of Europe, prescription melatonin at 2mg is the available form, and the over-the-counter market is smaller.
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Frequently asked questions
When should I take melatonin?
It depends on your goal. For sleep onset difficulty, take 0.5mg at your DLMO, roughly 2 hours before your target sleep time. For shifting your clock earlier, take 0.5mg 5 hours before your current DLMO (about 7 hours before your current bedtime). For jet lag flying east, take it at the destination's target bedtime on arrival day. Most people take melatonin at the wrong time (at bedtime, when the natural rise has already begun) and at too high a dose.
What is DLMO?
DLMO (Dim-Light Melatonin Onset) is the moment when your body begins producing melatonin in earnest, the biochemical signal that darkness has arrived and sleep should follow. It typically occurs about 2 hours before habitual sleep onset. DLMO is the cornerstone of circadian phase assessment in clinical sleep medicine. Taking melatonin supplements timed to this window amplifies the natural signal without creating the pharmacological sedation or phase errors that come from mistimed doses.
What dose of melatonin should I take?
0.5mg is the evidence-backed dose for circadian effects. Most commercial melatonin products (3–10mg) are 6–20 times higher than needed. Brzezinski et al. (2005) showed that 0.5mg was as effective as 3mg for shifting the circadian clock in phase advance protocols. High doses cause a large immediate spike that clears quickly, while low doses provide a more physiological profile. Start at 0.5mg, you can always increase, but you can't undo the overshoot.
Does melatonin make you sleep?
At physiological doses (0.5mg), melatonin has a weak direct sedating effect, it is primarily a timing signal, not a sleeping pill. It tells the brain that darkness has arrived, but it does not cause sleep the way sedatives do. At pharmacological doses (5–10mg), there is more sedation, but this comes with greater risk of phase disruption and morning grogginess from residual melatonin. If you find that even 0.5mg makes you feel groggy the next morning, you may be particularly sensitive to its phase-shifting effects.
Not medical advice. Consult a physician before use if pregnant, under 18, or on medication.