How long will antibiotics affect birth control?

According to Student Health Services at Ohio State University and the National Center for Biotechnology Information, most antibiotics do not interfere with the effectiveness of birth control pills. The only antibiotic proven to interact with the birth control pill (as well as the birth control patch and vaginal ring) is rifampin.

While antibiotics generally don't interfere with birth control, OSU recommends using a non-hormonal form of contraceptive, such as a condom, when having sex for extra protection even when on birth control. Some medications, including phenytoin and carbamazepine, do affect the reliability of the birth control pill, so women must consult with a doctor when starting new drugs if they are on birth control.