Can I Take Antibiotics and Birth Control?

FACT CHECKED

“Use a backup method, just in case.”

If you’ve ever been prescribed an antibiotic while taking birth control, you may have heard this advice. It’s been repeated for decades. But does it still hold true? 

The short answer: Current evidence suggests that most antibiotics, including commonly prescribed drugs like amoxicillin, amoxicillin–clavulanate (Augmentin), and azithromycin (Zithromax), do not interfere with birth control.

The concern started more than 40 years ago, when early research suggested that antibiotics might affect how the body processes oral birth control, fueling a widespread belief that they could reduce its effectiveness. However, according to current clinical guidance, most antibiotics do not appear to interfere with hormonal birth control — outside of two important exceptions.

What The Research Really Shows: Antibiotics and Birth Control Rarely Interact

“Common antibiotics don’t interact with birth control,” says Aparna Sridhar, M.D., an associate clinical professor of obstetrics and gynecology at the UCLA David Geffen School of Medicine.

Both the American College of Obstetricians and Gynecologists (ACOG) and the Centers for Disease Control and Prevention (CDC) generally agree that most broad-spectrum antibiotics are unlikely to interfere with the effectiveness of most birth control, including pills, patches, implants, and vaginal rings.

That said, large clinical trials specifically examining this interaction have not been conducted, largely because they would raise ethical concerns. Intentionally testing for possible birth control failure could expose participants to unintended pregnancy, even if the risk is expected to be low.

Still, the evidence we do have is strong. Researchers have studied this interaction in a few ways:

• Studies that measure drug levels in the blood. Research shows that estrogen and progestin levels remain stable in individuals taking birth control pills alongside common antibiotics
• A review of six clinical trials and three observational studies found no increase in pregnancy rates among women using hormonal birth control while taking antibiotics.
• A large case-crossover study of almost 18,000 women found no link between antibiotic use and unintended pregnancies, though the authors cautioned that study limitations prevented them from definitively ruling out oral contraceptive failure. 

Larger reviews have not found higher rates of unintended pregnancies during periods of antibiotic use compared with control periods. If antibiotics truly made these birth control methods less effective, higher pregnancy rates would be expected

The bottom line: For most antibiotics, the risk of impacting birth control effectiveness is very low — unless you take rifampin or rifabutin (Mycobutin). More on that later.

How the Myth Started, And Why It Stuck Around

The idea that antibiotics might interfere with oral birth control first appeared in the 1970s. Over the subsequent decades, case reports identified women who became pregnant while taking antibiotics while on birth control pills.

Case studies, which are detailed reports of individuals with medical events, are useful for spotting new or unexpected developments. But they don’t show that one thing caused another. And the findings from a small number of cases can’t be applied to the wider population.

Lowering blood levels of estrogen and progestin can make birth control less effective. The main explanations for how antibiotics can interfere with oral birth control methods are:

• Gut bacteria disruption. Some bacteria in the intestines help maintain estrogen levels. Antibiotics may kill these bacteria, lowering estrogen in the blood.
  
• Liver enzyme changes. Enzymes called cytochrome P450s (CYP450s) are proteins that help the liver break down sex hormones like estrogen and progestin. Some drugs can induce those enzymes, accelerating the metabolism of estrogen and progestin and lowering circulating hormone levels. Most commonly used antibiotics, however, do not meaningfully induce these enzymes.

A 2020 Study Causes Confusion

A recent analysis further contributed to the concern surrounding this topic. In a review of almost 75,000 reports of drug side effects, British researchers found that unintended pregnancies were more often reported among women taking antibiotics. The study made the news, but it apparently had major flaws:

• The researchers did not actually confirm that everyone who reported a pregnancy while on antibiotics was actually using contraception. 
  
• The data relied entirely on self-reports of pregnancies. This can’t show cause and effect (in this case, that taking antibiotics led to birth control failure).

Despite Evidence, Antibiotic Labels Still Come With Warnings

Perhaps due to a “better safe than sorry” approach, some antibiotic labels still warn about interactions with birth control. Removing warnings could expose drug manufacturers to lawsuits if a pregnancy occurs, even if antibiotics aren’t to blame.

As long as the labels carry them, it’s easy for the myth to stay alive. When providers and patients read a warning on a drug label, it feels true — even if current evidence tells a different story.

The Exceptions to Know About: Rifampin and Rifabutin

There is one important exception, however, a group of medications called rifamycins, specifically rifampin. Rifabutin (Mycobutin) can also reduce birth control effectiveness, but to a lesser degree. 

Rifampin (Rifadin) is most often used to treat tuberculosis. Rifabutin is approved for the prevention of certain infections in people with HIV. 

“Rifampin is what’s known as a strong inducer of certain CYP450 enzymes,” says Emily Kaip, PharmD, a pharmacist specialist in infectious diseases at the University of California, San Francisco. By doing so, rifampin speeds up how quickly the body breaks down some medications, including the hormones in combined oral contraceptives. “This lowers hormone levels below what’s needed for effective contraception,” says Dr. Kaip, “making pregnancy more likely.” 

Rifabutin has a similar effect but to a lesser degree.

Although most research focuses on oral birth control pills, the effectiveness of other hormonal methods may also be affected. This includes hormonal patches (Xulane, Twirla), vaginal rings (NuvaRing, Annovera), and the progestin-only implant (Nexplanon). However, IUDs (Mirena, Kyleena) and the progestin-only injection (Depo-Provera) aren’t known to be affected, says Dr. Sridhar. IUDs act directly on the uterus, and the injection delivers a high enough dose of progestin that rifampin’s impact is less significant.

Even though there aren’t large studies directly showing higher pregnancy rates, the mechanism described above is clear. Thus, the recommendation is to use a backup method, like condoms or an IUD, while taking these antibiotics. And you may need to continue it for up to 28 days after stopping the antibiotic. Talk to your healthcare provider to ask exactly how long to continue it.

How to make sure you’re protected

If you’re taking an antibiotic other than rifampin or rifabutin, you probably don’t need to do anything differently. Talk to your prescriber if you’re worried, though. They can help you feel confident and protected. And consider these tips for maximum protection:

• Take your birth control as prescribed. Missed or late pills are more likely to cause an unintended pregnancy than antibiotic use. If you struggle to take your pill consistently, consider a long-acting birth control method like an implant, injection, or IUD.
  
• Watch for vomiting or severe diarrhea. Antibiotics can cause nausea, vomiting, and diarrhea. If you can’t keep your pill down within two hours of taking it, or if you’ve had diarrhea for 24 hours or more, consider it a missed dose, says Dr. Kaip. You may need to use backup contraception. How long to use it for may vary from product to product. So check with your healthcare team about what to do.
  
• Ask about other medication interactions. Give your medical provider a list of all your medications, including over-the-counter products. They can let you know if anything you take interacts with the birth control method you are using.

Keep in mind: Even though most antibiotics don’t interfere with birth control, that doesn’t mean either medication is risk-free. Every contraceptive method carries its own potential side effects, separate from antibiotic use. So it’s worth asking about risks when discussing options with your healthcare team. Antibiotics also carry their own risks, and some drug classes are best avoided for mild infections. Fluoroquinoline antibiotics are one example, which includes medications like ciprofloxacin (Cipro). Always ask why a specific antibiotic is being prescribed and what side effects to watch for.

Summing it all up

Most antibiotics don’t affect birth control effectiveness. 

The key exceptions are rifampin and rifabutin, which can lower hormone levels and make hormonal birth control methods less effective. These include pills, patches, vaginal rings, and the progestin-only implant. However, IUDs and the progestin-only shot aren’t affected by rifampin and rifabutin.

If you’re prescribed these specific antibiotics, use a backup method like condoms or an IUD during treatment and for a period afterward. Ask your healthcare team how long to continue backup protection.

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