The time it takes for birth control to be effective depends on the type of method used:

• For birth control pills:
  • Combination pills (contain estrogen and progestin): If started within 5 days of the first day of the period, they work immediately. If started at any other time in the cycle, it takes 7 days to become effective.
  • Progestin-only pills ("mini-pills"): If taken within the first 5 days of the period, they work immediately for typical cycles. For shorter cycles or if started after 5 days, it takes 2 days to become effective.
• Other methods:
  • Intrauterine devices (IUDs) with copper work immediately.
  • Hormonal IUDs and implants work immediately if inserted within the first 5 days of the cycle; otherwise, they take 7 days.
  • Birth control shots work immediately if given within 5 days of the period starting; otherwise, they take 7 days.
  • Barrier methods (condoms, diaphragm, spermicide) work immediately when used correctly.
  • Sterilization methods (vasectomy, tubal ligation) can take months to be fully effective.

In summary, most hormonal contraceptives take from immediately up to 7 days to be effective, depending on timing and type. Barrier methods work immediately. Using a backup contraceptive method for 7 days is recommended unless the method works immediately upon starting within the early days of a menstrual period.