Birth control pills take different amounts of time to become effective depending on the type and when they are started during the menstrual cycle:
- Progestin-only pills (mini-pill) can be effective immediately if started within the first 5 days of the menstrual cycle (usually the first day of the period). If started after day 5, it takes about 2 days to become effective.
- Combination pills (contain estrogen and progestin) are effective immediately if started within the first 5 days of the period. If started at any other time, it takes 7 days to become fully effective, so backup contraception is recommended during this first week.
For both types, starting after childbirth or pregnancy loss has specific recommendations but generally they start working immediately or within a few days if started promptly. In summary, birth control pills can take anywhere from immediate effectiveness to up to 7 days, depending on the type and timing of when the pills are started in the menstrual cycle.
