The birth control pill's effectiveness depends on the type of pill and when it is started in the menstrual cycle:
- Combination pills (contain estrogen and progestin) are effective immediately if started within the first 5 days of the menstrual cycle (day 1 is the first day of the period). If started at any other time, they take 7 days to become effective, so back-up contraception should be used for those 7 days.
- Progestin-only pills (mini-pills) can be effective immediately if started in the first 5 days of the menstrual cycle, but otherwise take 2 days to become effective, requiring back-up contraception during that time.
It is important to take the pill consistently at the same time each day to maintain effectiveness. Missing doses or taking the pill late can reduce effectiveness and may require additional contraception for 7 days. In summary, protection can start immediately if the pill is started during the first 5 days of the cycle; otherwise, it usually takes 2 days for progestin-only pills and 7 days for combination pills to become fully effective.
