The time needed for birth control to be effective depends on the type:
- For combination birth control pills (which include estrogen and progestin), if taken within the first 5 days of the menstrual period, the pill works immediately. If started at any other time in the cycle, it takes 7 days to become effective, during which backup contraception should be used.
- For progestin-only pills ("mini-pill"), if taken within the first 5 days of the period, it starts working immediately. Otherwise, it takes about 2 days to become effective, and backup contraception is advised for those 2 days.
- Other methods vary: barrier methods like condoms work instantly, while IUDs, implants, and shots have different timelines depending on when they are started.
Thus, for birth control pills, it is critical to use backup contraception for about 7 days if the pill is not started at the beginning of the period.
