Why are some medicines taken weekly rather than daily?

Whether a medicine is taken daily or weekly comes down to how long it remains active in the body. Some are cleared within hours and need topping up daily; others are designed to persist for days, which allows a weekly schedule.

That difference changes what a missed dose means. With a daily medicine the gap is short. With a weekly one, the instructions for what to do about a missed dose are specific to that product and appear on its label, which is why the answer is in your leaflet rather than in general advice.

It also explains why a weekly medicine does not stop working the moment you skip one, and equally why doubling up is not the fix. Those are precisely the situations the label addresses directly, and a pharmacist can walk you through yours.