How long does it take for birth control to go back to normal when taking antibiotics?

Possible interaction: Some evidence suggests that some people may have lower blood levels of the hormones in bc pills if you take antibiotics, but other studies show that many people do not have lower blood levels. To minimize the risks of bc failure, use a backup method such as condoms during the cycle you're taking antibiotics. If you take antibiotics daily, discuss this with your doctor; there's not much evidence.