How long does Melatonin 1mg
stay in your system?

A 1 mg melatonin tablet sits close to what sleep research suggests is the effective range for shifting circadian timing. Studies repeatedly find no added benefit from doses above roughly 0.5 to 1 mg for resetting the body clock; higher amounts mainly add grogginess rather than stronger timing effects.

With melatonin's very short half-life of around 45 minutes, even this small dose drops to a trace within a few hours. What keeps you asleep afterward is your own sleep architecture, not lingering melatonin, since the supplement itself has largely cleared before the night is over.