Why does melatonin timing matter more than just taking a bigger dose for jet lag?

Answer: It marks body-night

Dose sets direction — A larger dose does not choose whether the clock should move earlier or later. The useful direction comes from timing: travel guidance treats eastward and westward use differently. This is why "take more" is the wrong mental model; a small, well-timed dose can matter more than a large, poorly timed one.

It marks body-night ✓ — Melatonin is read by the body as a signal of darkness, so it acts like a biological timestamp. Used at the right time, it can help your clock accept night at the destination instead of clinging to home time. The memorable twist is that Mayo notes even 0.5 mg can be effective when timing is right.

It repays sleep debt — Melatonin is not a repayment account for sleep debt. It may help you sleep at an unusual time, but the jet-lag value comes from telling the clock when night should be. That is why both Mayo and CDC emphasize timing rather than simply recommending the largest possible dose.