When does birth control start working?

Hormonal birth control starts working one week after initiation. This is true for all types of birth control containing hormones–pill, patch, ring, progestin IUD, shot, and implant. The copper IUD is different: it starts to work immediately. 

The secondary benefits of some hormonal birth control (i.e., acne improvement, decreased menstrual bleeding) typically take effect within one-to-three months. 

Ovulation can occur within one-to-two weeks of stopping the pill, though it often takes longer (up to three months) to get back into a regular ovulatory rhythm. Exactly when ovulation will resume for any particular person is unpredictable.