How long after stopping antibiotics does birth control work

Medically Reviewed By William C. Lloyd III, MD, FACS

— Written By Megan Freedman

Updated on August 4, 2020

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Do you know that you can get pregnant while taking antibiotics, even if you’re taking birth control pills? Not all antibiotics have this effect. But to be safe, before starting an antibiotic, tell your healthcare provider that you are on the pill and ask if you should use a backup form of birth control temporarily.

How do antibiotics affect birth control pills?

The birth control pill, commonly called “the pill," is a medication women take once a day to prevent pregnancy. One way birth control pills prevent pregnancy is by preventing ovulation—when your body releases an egg that can be fertilized by a male sperm. Some antibiotics can interfere with your menstrual cycle, causing you to ovulate even though you’re on the pill.

Which antibiotics are more likely to interfere with the pill?

Not all antibiotics will increase your chances of getting pregnant on the pill. However, one particular antibiotic, called rifampin (Rifadin, Rimactane), can interfere with your menstrual cycle and reduce the effectiveness of birth control pills. While rifampin is less commonly prescribed today, other types of medications may also have the same effect. These include the antifungal griseofulvin, antiretrovirals, and the herbal remedy St. John's Wort.

You may wonder how an antibiotic could possibly affect your birth control pill. In the case of rifampin, scientific studies have shown that it decreases blood levels of both ethinyl estradiol and the progestins contained in birth control pills. If their blood levels fall too low, the hormones can’t do their job of preventing ovulation. The mechanism is complex, but basically rifampin stimulates your liver to process and get rid of these hormones faster than normal.

The data are not so clear for other antibiotics, so the interaction remains controversial. Unlike rifampin, there aren’t conclusive scientific studies for other antibiotics. But there are various theories about how other antibiotics might interfere with your birth control pill. Some of these theories are even more complex than rifampin’s interaction. Basically, the theories suggest that antibiotics may decrease the amount of hormones your body absorbs. However, none of them are solidly proven.

Talk with your healthcare provider or pharmacist before starting an antibiotic. Ask if it will change the effectiveness of your birth control pills or other hormone-based birth control you may be taking, such as an implant, shot or patch. If you have any worries or doubts about taking an antibiotic with your birth control pill, be safe and use a backup method of birth control. It can’t hurt and it may put your mind at ease.

How can I prevent pregnancy if I'm taking antibiotics?

It is not likely that you will get pregnant while taking antibiotics on the pill. But it doesn't hurt to be extra cautious. To be safe, use a backup method of birth control while you take your antibiotics and for up to a week after you finish. Backup birth control options you can try include condoms, sponges and spermicide. You can buy these forms of birth control without a prescription at many grocery stores and drugstores.

Do not stop taking your birth control pills even if you are temporarily using a backup method of birth control. Take your pills exactly as you always have to avoid messing up your cycle.

Top things to know

• Most antibiotics will not interfere with your hormonal birth control method

• Only rifamycins, including rifampin, will make your birth control less effective

• If you are prescribed rifampin, be sure to use back-up protection like condoms or abstain from sex

I’m on hormonal birth control. Can I get pregnant if I take antibiotics? 

In most cases, no, as long as you continue to use your hormonal contraception as prescribed you are safe from pregnancy even if you are on antibiotics. 

It is a myth that all antibiotics will interfere with the efficacy of your birth control pill. 

There is however, one class of antibiotics that is the exception: rifamycins (1). 

What do I need to know about Rifamycins?

Rifamycins are a class of antibiotics. The most commonly prescribed rifamycin is known by the name rifampin. (Other types of rifamycins include rifapentine, rifabutin, and rifaximin.) Rifampin is not prescribed very commonly in the United States. 

Rifamycins, are most commonly prescribed for the treatment of mycobacterial infections, including tuberculosis (1), or for treating travelers’ diarrhea caused by E. coli (2). 

Rifampin can sometimes be used in combination with other antibiotics to treat other bacterial infections too (1). (Fun fact about rifampin: one of the side effects is that it may turn your urine, tears, saliva, and sweat a red color (3).) 

Rifampin, can speed up the liver’s ability to break down molecules and medications, including hormonal birth controls, which are processed continually through the liver (3). 

For this reason, anyone taking any form of hormonal contraceptive, like the pill, patch, ring, mini-pill, and the implant, who is prescribed rifampin treatment should note that their hormonal contraceptive will not be as effective, and may increase their likelihood of becoming pregnant (3-5). 

Rifampin does not interact with other forms of birth control, such as the contraceptive shot, the copper IUD, and the hormonal IUD, meaning that you can continue to use these types of contraception while undergoing rifampin treatment (4,5). 

What if my healthcare provider prescribes rifampin for me?

If your healthcare provider does prescribe rifampin to you, be sure to let them know if you are using a hormonal contraceptive. 

Unless otherwise stated by your healthcare provider, you can still continue to take your pills as usual every day. However, during this time, it’s important to use non-hormonal birth control methods, like external or internal condoms, or abstain from sex as backup protection during rifampin treatment (3). 

If you use birth control pills, consider following the recommendations for what to do if you miss two or more pills: 

• Continue to use these non-hormonal backup methods for 7 days after you stop taking rifampin, provided you still have 7 hormone-containing pills left in your pack

• If there are fewer than 7 hormonal pills left in the pack after you stop taking rifampin, skip the hormone-free pills and start a new pack, but still continue to use back-up contraception for the first 7 pills of the pack (6). 

If you are using another form of hormonal contraceptive, like the patch or ring, speak to your healthcare provider. 

Things to keep in mind, when you’re sick 

Even if you aren’t on rifampin, being ill is hard on the body and mind. If you are sick, it’s easy to lose track of time and responsibilities, and you might forget to take your pill (or other daily medication). Use Clue to set up pill reminders, or task a family member, partner, or friend, to help remind to make sure to take your contraceptive pill daily at the same time. 

Use the Clue app to set up daily pill reminders.

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