Family Planning Plus

Pregnancy is highly unlikely as long as you have been using your birth control as directed. To be extra cautious, we do recommend that our patients use condoms in addition to their regular hormonal method when they are also using antibiotics. The effectiveness of any type of estrogen-containing birth control pill may be impaired during treatment with some types of antibiotics.  However, the risk is very slight, and the supportive evidence is primarily limited to anecdotes from case reports and findings from uncontrolled or poorly controlled studies.  In fact, according to Contraceptive Technology, 19th Edition, it is not necessary to use a back up method of birth control while on antibiotics because they do not lower the levels of hormones in your blood to the point that you would be at risk for pregnancy.  The only exception is the medication, rifampin (which is primarily used to treat tuberculosis).   

Since no birth control method is 100% effective, however, pregnancy is always a possibility. Keep using your birth control as directed. If you are a week or more late for your next period, take a pregnancy test. Use first morning urine for the best results. If it is negative, repeat the test every two weeks until you have a normal period or a positive test result. Do not stop using your regular method of birth control unless you test positive for pregnancy.