Antibiotics and Birth Control Pill Interactions: Fact or Fallacy?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Jan 30, 2022.

Can you take antibiotics with birth control?

Should you use a barrier back-up method of birth control (such as a condom) while you are also taking an antibiotic with a hormonal form of contraception?

For many years, women have been counseled that their birth control might become less effective if they also took a course of an antibiotic at the same time. The usual advice to women from healthcare providers was to add a barrier form of birth control (like a condom or diaphragm) to their contraceptive and for a period of time after finishing the antibiotic to help prevent pregnancy.

Today, most research states that antibiotics, with the exception of the tuberculosis drug rifampin (also known as Rifadin and Rimactane) and possibly other rifamycins like rifabutin (Mycobutin), do not alter the effectiveness of hormonal forms of birth control that are absorbed into the blood (for example pill, patch or vaginal ring). However, critics maintain that many studies that have found a lack of an interaction have been small and therefore unlikely to detect infrequent interactions.

In contrast, a large but observational database study from BMJ Evidence-Based Medicine published in August 2020 suggests that there is a possibility of pregnancy when birth control and antibiotics are combined. However, this study cannot prove a cause and effect outcome based on the retrospective design and limitations of the research.

Because some studies are conflicting, you should discuss this topic with your healthcare provider if you are prescribed an antibiotic and you use a hormonal form of birth control.

• It is reported that birth control pills fail 1% of the time when used perfectly and 9% of the time with typical use. This means, with normal use, about 9 out every 100 women may still become pregnant each year using the pill.
• Many women are not willing to accept the added chance of pregnancy when using antibiotics, especially with conflicting study data.
• On the other hand, some women don't relish the thought of an added barrier method of birth control for one or two weeks, or even longer.
• Talk to your doctor. Your healthcare provider may still recommend that you use an added method of birth control (for example, a condom and spermicide or diaphragm and spermicide) to your hormonal method during a short course of antibiotic treatment.

What does the research say?

According to the clinical advice, experts and women’s health providers, only one antibiotic - rifampin (brands: Rifadin and Rimactane), and to a lesser extent rifabutin - have been proven to make the birth control pill less effective.

• Rifampin lowers the effectiveness by decreasing the birth control hormone levels (ethinyl estradiol and progestin) in women taking oral contraceptives. The hormone levels are needed to prevent ovulation.
• Rifampin can induce enzymes in your liver that will break down estrogen faster than normal. Lowering hormone levels can reduce the effectiveness of your birth control.
• Rifampin can also lower the effectiveness of the transdermal birth control patch (Ortho Evra, Xulane) and the vaginal ring (NuvaRing, EluRyng, Annovera), so an added barrier method of birth control should be used with these products.
• A nonhormonal method of birth control - for example, a condom, diaphragm, or copper IUD, is recommended with rifampin use. Depo-Provera, the birth control shot, may be another option.

A 2018 review published in the American Journal of Obstetrics and Gynecology concurred with this information. Researchers completed a literature review of multiple studies that met inclusion criteria. The authors concluded that most women can expect no reduction in effectiveness with the use of hormonal contraceptives and antibiotics (except for rifamycins).

A review from the Journal of the American Academy of Dermatology states that pharmacokinetic evidence demonstrates that levels of oral contraceptive steroids are unchanged with combined administration of antibiotics, including:

• ampicillin
• ciprofloxacin
• clarithromycin
• doxycycline
• metronidazole
• ofloxacin
• roxithromycin
• tetracycline

Even with this study data and expert opinions, the association between antibiotic use and contraceptive failure is still controversial. Large clinical trials have not been completed, but many individual studies have been evaluated. Some experts argue that studies are too small or poorly designed to determine the interactions between individual antibiotics and birth control.

In August 2020, researchers from the UK published a controversial, observational "database" study in BMJ Evidence-Based Medicine. This study suggested (but could not prove) that antibiotics may lower the effectiveness of hormonal contraceptives, including the pill.

• Researchers reviewed an analysis of reported unwanted side effects (called Yellow Cards in the UK) and found that unintended pregnancies were 7 times more likely for those taking antibiotics than for other types of unrelated drugs.
• The authors concluded that women on hormonal contraceptives should be advised to use extra precautions to avoid unintended pregnancy when prescribed antibiotics.
• However, this study has been criticized based on its study design and need for recall bias.

What other types of drugs can alter birth control effectiveness?

Other drugs besides rifampin or the rifamycins may affect birth control reliability. Other drugs that induce enzymes can affect hormonal levels of your birth control and may lower its effectiveness.

Therefore, always have your doctor or pharmacist complete a drug interaction review any time you start or even stop a medication. This includes prescription medicines, as well as over-the-counter (OTC) drugs, vitamin and herbal or dietary supplements.

For example:

• The antifungal medicine griseofulvin may lead to lower levels of birth control hormones and reduce the effectiveness of birth control pills.
• Certain seizures drugs can also lower the effectiveness of combined birth control pills, for example anticonvulsant medications such as:
  • carbamazepine (Tegretol)
  • phenytoin (Dilantin)
  • primidone (Mysoline)
  • topiramate (Topamax, Qudexy XR)
  • felbamate (Felbatol)
  • oxcarbazepine (Oxtellar XR, Trileptal)
  • and barbiturates like phenobarbital
• Some HIV medications, such as efavirenz, protease inhibitors, or antiviral boosters may also affect birth control effectiveness.
• Two small studies suggest that St. John's wort can induce liver enzymes, which may increase birth control pill metabolism and reduce therapeutic efficacy. This may be possible with the patch and birth control ring, too.

If you’re taking any of these drugs use condoms (or other reliable barrier method) as a backup form of birth control. Talk to your doctor about switching to a different nonhormonal method of birth control (for example: the copper IUD or a diaphragm) if you’ll be on these interacting drugs for a long time.

This is not a complete list of all possible interactions with birth control. Use the Drugs.com Interaction Checker to review for possible drug interactions with your birth control method and review them with your doctor or pharmacist.

And remember, the main reason women get pregnant when using the pill is because they do not take it correctly. Learn more: Missed taking your birth control pill? Here's what to do next

• Birth control pills fail at least 1% of the time in perfect conditions, and up to 9% of the time with typical use, so taking your pill as directed or faithfully using other reliable contraceptive methods are the key to pregnancy prevention.
• Other events, such as vomiting or having diarrhea for more than 48 hours may also lower how well the pill prevents pregnancy, too.

See Planned Parenthood for more information.

See also

• Alcohol and Antibiotic Interactions
• Antibiotic Resistance: The Top 10 List
• Antibiotic Shortages: A Serious Safety Concern
• Antibiotics - Common Side Effects, Allergies and Reactions
• Antibiotics for UTI Treatment
• Middle Ear Infection FAQs (Acute Otitis Media)
• Why Don’t Antibiotics Kill Viruses?

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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