Medically reviewed by Dr. Julie Graves, MD, MPH, PhD on January 13, 2020
Most antibiotics (medications designed to fight bacterial infections) do not affect your birth control, with the exception of a few. While some women have gotten pregnant while taking antibiotics and hormonal birth control at the same time, these reports are rare. Your chances of getting pregnant while taking most types of antibiotics are no higher than the normal failure rate of birth control, which is 6 to 9%.
How Antibiotics Might Affect Birth Control
Some types of antibiotics have the potential to affect birth control because they can alter the body’s hormone levels. Hormonal birth control methods that these antibiotics might impact include:
- The pill
- The patch
- The ring
- The shot
All four of these birth control methods contain the hormones estrogen and/or progestin which thickens the mucus in the cervix, making it difficult for sperm to fertilize an egg, and thin the lining of the uterus to reduce the chance of getting pregnant. The methods that contain estrogen also prevent you from ovulating, while progestin-only methods stop ovulation but not consistently. Certain antibiotics can lower the levels of estrogen and progestin in your body, potentially to the point of affecting your birth control.
Theoretically, antibiotics might also reduce your birth control’s efficacy by interrupting the recirculation of estrogens in the body — a process called enterohepatic circulation. They do this by killing the bacteria in the small intestine that help break the hormone down and redistribute it within the body.
For these reasons, many manufacturers have historically placed warnings on antibiotic labels to inform women about this risk. Over the years, scientists have done many studies on various types of antibiotics’ effects on hormonal birth control to determine which ones you should and should not take at the same time.
Antibiotics That Can Affect Birth Control
Researchers have only proven that two types of antibiotics can affect the efficacy of your birth control:
- Rifampin: Health care providers prescribe this medication to treat tuberculosis. Rifampin causes the enzymes in your liver to break estrogens down faster than normal, lowering those hormone levels in your body and possibly reducing your birth control’s efficacy. Some women might experience spotting between their periods while taking rifampin, but this doesn’t mean their birth control isn’t working.
- Rifabutin: Health care providers prescribe this medication to prevent an infection called mycobacterium avium complex in HIV patients, as well as to treat tuberculosis. It, too, reduces the levels of birth control hormones that suppress ovulation but to a lesser degree than rifampin.
Both of these medications belong to a class of antibiotics called rifamycins. Scientists have not been able to prove that any other rifamycins, however, affect birth control.
Antibiotics That Do Not Affect Birth Control
Most antibiotics have no proven effects on hormonal birth control and will not increase your chances of getting pregnant if you have sex during treatment. Commonly prescribed antibiotics that are safe to take while on birth control include:
- Ampicillin, for treating bladder infections, pneumonia, and more.
- Cephalexin, for treating upper respiratory, ear, skin, urinary tract, and bone infections.
- Ciprofloxacin, for treating skin, respiratory, joint, and urinary tract infections.
- Clarithromycin, for treating bacterial skin and respiratory infections.
- Clindamycin, for treating skin, lung, soft tissue, vaginal, and pelvic infections.
- Doxycycline, for treating urinary tract infections, gonorrhea, chlamydia, syphilis, respiratory infections, and more.
- Metronidazole, for treating vaginal, stomach, liver, skin, joint, and respiratory system infections.
- Minocycline, for treating urinary tract, respiratory, and skin infections, as well as chlamydia.
- Ofloxacin, for treating skin infections, urinary tract infections, pelvic inflammatory disease, chlamydia, and gonorrhea.
- Roxithromycin, for treating bacterial respiratory tract, urinary and soft tissue infections.
- Sulfamethoxazole, for treating urinary tract, ear, and respiratory infections, among others.
- Tetracycline, for treating skin, respiratory, urinary, and other infections, as well as syphilis, gonorrhea, and chlamydia.
- And many more.
Other medications that aren’t antibiotics, such as some antifungals, might have interactions with your birth control too, so always tell your health care provider about all the medications you’re taking.
What to Do if You Need to Take Antibiotics While on Birth Control
If your health care provider prescribes you an antibiotic and you’re concerned about it affecting your birth control, simply use a backup form of birth control during and a week after treatment. These include:
- A diaphragm (a silicone cup placed in the vagina).
- Spermicide (a substance that kills sperm).
- A cervical cap (similar to a diaphragm but smaller).
You might also talk to your medical team about switching to nonhormonal birth control, such as a copper intrauterine device (IUD). This small device can be placed in your uterus to prevent sperm from reaching and fertilizing an egg. The copper essentially acts as a spermicide.
If your health care provider prescribes you a rifamycin, always use a backup method of birth control, such as a condom or diaphragm, when having vaginal sex. Use one of these backup methods for the entire length of your treatment, plus a week after finishing the antibiotic.
If you are taking an antibiotic to treat a sexually transmitted infection such as gonorrhea or chlamydia, then you might need to avoid having sex during and immediately after treatment. Your Nurx™ medical provider can provide with the exact recommendations for each.