When does birth control pills become effective?

7 days: Most doctors recommend 7 days of birth control pills before having unprotected intercourse. Even with pills, there is still a 4-6% chance of pregnancy over course of a year. If miss 1 pill, take that pill immediately the next day with that days pill. If miss 2 days pills, take 3 pills and use back up method until you get your period.

Ocp effectiveness: When taken as directed, birth control pills are usually effective the first month you begin taking them. To be safe, some doctors recommend the use of another form of birth control, such as condoms and foam, during the first month. After the first month, you can just rely on the pill for birth control.

Immediately: Birth control pills are 90% effective right away and 99% in 1 week assuming you are not pregnant when you start taking them. Realize that there are a lot of other consequences to having intercourse that birth control pills won't prevent. If you are having unprotected sex you need to be checked for std. You can't trust your partner to know. If you have pain, see a doctor right away.