Supplement
How long does Melatonin 5mg
stay in your system?
A 5 mg melatonin tablet — one of the most commonly purchased doses, though evidence suggests most people don't need more than 0.5–1 mg for sleep onset.
Based on Melatonin half-life · 45 minutes
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A 5 mg melatonin tablet is a popular strength but well above what circadian research suggests is needed for shifting sleep timing. The extra milligrams do not reset the body clock more effectively; they mostly increase sedation and the chance of feeling groggy the next morning.
Even at 5 mg, melatonin's roughly 45-minute half-life clears the dose to a trace within a few hours. By the time you wake, even a 10 mg dose has passed through six or more half-lives, so leftover melatonin is rarely the real cause of morning heaviness.