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Hi, i’ve been on antibiotics for almost a year for acne and I recently went on birth control. I know that antibiotics lessen the effectiveness of the birth control, so I was wondering how long I would have to wait after stopping the antibiotics in order for them to get out of my system and be able to have safe sex. Also, how long after starting the birth control should I wait?

Only one antibiotic is known to make the pill less effective. That is rifampin, a special medication used to treat tuberculosis. The brand names include Rifadin and Rimactane. Other antibiotics do not make the pill less effective. So you can use your acne antibiotics with birth control pills, and both medications will be effective.

In terms of when your birth control pills will start protecting you against pregnancy, it depends on whether you’re taking combination pills or progestin-only pills.

If you start combination pills within five days after the start of your period, you are protected against pregnancy right away. You will not need to use a backup method of birth control. That means that if your period starts on a Wednesday morning, you can start the pill up to Monday morning to be protected right away. If you start at any other time during your menstrual cycle, you will be protected from pregnancy after seven days. Use another method of birth control — like a condom, female condom, diaphragm, or sponge — if you have vaginal intercourse during the first week of use.

You may start the progestin-only pill at any time. Use another method of birth control if you have vaginal intercourse during the first 48 hours of progestin-pill use — protection will begin after two days.

Learn more about the pill.

Tags: the pill, birth control, acne