When is the best time to start birth control?

With your period.: If you have regular monthly menses and you start your pills when you start your period, you will be protected from when you start the pills. If you start the pill at any other time during your cycle, then you should use some other form of birth control for at least two weeks before you will be protected. You should expect to have some spotting possibly for a couple months after starting the pill.

Before having sex: If you are planning to start on hormonal contraceptives it is best to start them at least 1 month prior to having sex. Things like condoms or diaphragms don't need to be in place till right before you have sex but still need to be in place before there is any genital contact. Remember the hormonal contraceptives don't prevent sexually transmitted diseases.