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Do Antibiotics Affect Birth Control?

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Do Antibiotics Affect Birth Control?

writtenByWritten by: Andy Wong
Andy Wong

Andy Wong

Andy is the Chief Marketing Officer at PlushCare. He's passionate about advancing healthcare solutions and improving access to care via health technology.

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September 15, 2017 Read Time - 9 minutes

Do Antibiotics Affect Birth Control?

Discovered in the 1920s by Scottish physician Alexander Fleming, antibiotics have become a mainstay of healthcare, helping your immune system fight off infections. However, if your doctor has ever prescribed antibiotics, you may have been told that it may make birth control pills less effective.

In fact, many antibiotic information sheets come with warnings suggesting the same thing. In general, the answer is no, most antibiotics do not affect birth control, but it’s important to know which antibiotics do interfere with your birth control and to consult with a physician if you are unsure. Let’s take a closer look at antibiotics and birth control.

What are Antibiotics?

Antibiotics are a type of medication designed to neutralize bacteria by either:

  • Killing bacteria outright
  • Preventing bacteria from multiplying and spreading
  • Hampering vital processes that are necessary to sustaining bacteria

Different antibiotics work on different types of bacteria. Broad spectrum antibiotics, which include amoxicillin, levofloxacin, and gentamicin, are designed to affect a wide range of bacteria. Penicillin, azithromycin, and other narrow spectrum antibiotics affect only a few specific types of bacteria.

How Do Antibiotics Work?

Different antibiotics have different mechanisms of working. Some affect how bacteria operate, while others may break down bacterial cell walls. It’s important to remember that antibiotics are only effective against bacterial infections. That means it is ineffective against viral and fungal infections.

You should never take antibiotics to treat the common cold and flu, stomach flu, and other infections caused by a virus. Overusing or incorrectly using antibiotics may create “superbugs” that are resistant to conventional bacteria.

Aside from viral and fungal infections, antibiotics can be used to treat a wide range of bacterial infections and diseases, including:

What is the Birth Control Pill?

Birth control pills are a form of medication that can be taken once a day to prevent pregnancy. The pill comes in a variety of forms from different brands, offering an easy, convenient, and affordable option for contraception.

When used perfectly, the pill is 99 percent effective in preventing pregnancy, though in real life applications, the pill will prevent pregnancies 91 percent of the time, which is still an effective amount.

How Do Birth Control Pills Work?

Birth control pills work directly on a woman’s hormones to stop ovulation, which is the process wherein an ovary releases an egg. Without ovulation, there is no egg for a sperm cell to fertilize, so you can’t get pregnant. The pill also contains hormones that thicken cervical mucus. Thicker mucus lining the cervix makes it more difficult for sperm cells to swim up to an egg.

Birth control pills generally come in two forms. Combination pills contain the hormones estrogen and progestin and work by stopping ovulation, thickening cervical mucus, and thinning the lining of the cervix. Combination pills come in packs of 28 or 21. In both instances, only 21 are active pills, meaning they contain the hormones. With 28-day packs, the extra 7 pills contain no hormones but are designed to help you keep up the habit of taking a pill a day.

Combination pills have varying amounts of estrogen and types of progestin. Monophasic pills have the same amount of hormones for each day throughout the month. Other pills, like triphasic pills, vary the hormone dosage and concentration through the month.

Progestin-only pills were designed for women who are sensitive to estrogen. They work by thickening cervical mucus and thinning the uterine lining. They do not suppress ovulation like combination pills, but they are still just as effective. Progestin pills also come in packs of 28, but all 28 of the pills are active and contain progestin.

Do Antibiotics Affect Birth Control?

Yes and no. Antibiotics certainly have the potential to make birth control less effective. Some antibiotics can cause enzymes in the liver to break down estrogens faster, decreasing the level of estrogen in the body and reducing the effects of birth control pills.

Antibiotics may also potentially reduce the recirculation of estrogen throughout your body. Estrogen is broken down in the liver and converted into other chemicals that are then dispersed into your intestines. Bacteria inside your intestines take these chemicals and reform them into active estrogen that gets reabsorbed into the body. In theory, antibiotics can neutralize the bacteria that convert the chemicals back into estrogen, but studies have yet to prove that this can lead to unwanted pregnancies.

To date, the only antibiotic that is known to reduce the effect of birth control pills is rifampin, which is usually prescribed as a treatment for tuberculosis and infections that can lead to meningitis. Rifampin can decrease estrogen levels in your birth control pill, reducing the pill’s ability to suppress ovulation.

Rifampin can also affect hormone levels in vaginal rings and birth control patches. If you are on birth control and are prescribed rifampin, consider asking for an alternative or make sure to use a secondary form of birth control that is not affected by hormonal changes, like condoms.

Aside from rifampin, you should not have any problems taking an antibiotic while on birth control.

Other Things That Can Reduce the Effectiveness of Birth Control

Birth control is primarily affected by forgetting to take it every day, though vomiting and diarrhea over a period of 48 hours can also reduce the pill’s effectiveness. Other medications and supplements that can potentially reduce the effectiveness of birth control include:

  • St. John’s Wort, an herb often used as a treatment for depression
  • Some medications used for treating HIV
  • Some anti-seizure medications
  • Griseofulvin, a treatment used for fungal infections, including ringworm and athlete’s foot

The Benefits of the Birth Control Pill

The biggest benefit of the birth control pill (aside from effectively preventing pregnancy) is its convenience. It is not invasive (meaning you do not need to undergo any type of surgical procedure), and the small size of the packs means that you can take your pills on the go. As long as you take your pills correctly, you are protected from pregnancy all day.

If you decide that the time is right to have kids, you can simply stop taking the birth control pill. While it may take a few months for your period to return to its cycle from before your used the pill, you can still get pregnant as soon as you stop taking the pill.

Birth control pills can also help with your periods by making them more regular and easier to predict. The hormones in birth control pills can also help to ease the pain and discomfort of periods, reducing menstrual cramps and making your periods lighter.

Combination pills can also help to reduce or even prevent:

  • Acne
  • Premenstrual syndrome
  • Anemia (iron deficiencies)
  • Infections in the ovaries, uterus, and fallopian tubes
  • Thinning bones (osteoporosis or osteopenia)
  • Cancer of the endometrium and ovaries
  • Cysts in the ovaries and breasts

While birth control pills do offer a wide range of benefits, they do not prevent sexually transmitted diseases. This means you should still use a condom during sex and take the appropriate steps to lower your risk of contracting an infection.

How to Get Antibiotics

Antibiotics can only be prescribed by a doctor, but the process is simple enough. When you get sick, visit your doctor in-person or online. Your doctor will perform a physical examination, ask about the history of your personal health, and consider the symptoms you may be experiencing. That is often enough for your doctor to make an accurate diagnosis and prescribe antibiotics online or in-person.

However, if your doctor needs more information to make a diagnosis, they may order lab tests. These tests allow them to identify the specific bacteria infecting your body and prescribe the most effective antibiotic to neutralize the bacteria.

How to Use Antibiotics

Most antibiotics come in the form of pills or capsules that are taken orally, but some are injected, while others are topical and applied directly to the affected part of the body. You should feel the effects of antibiotics on your infection within the first few hours, and symptoms generally improve within the first day.

Some antibiotics should be taken on an empty stomach, usually about an hour before meals or two hours after meals. Some antibiotics should not be consumed in conjunction with certain foods and drinks. For example, you should not consume dairy while taking tetracycline as dairy products can affect how the antibiotic is absorbed. You should also avoid alcohol if you are taking metronidazole.

Most importantly, make sure you take the full course of antibiotics as prescribed by your doctor to completely eliminate the infection. Even if you feel better, you may still have bacteria in your system that can eventually grow and re-infect your body, leading to even more severe symptoms.

Stopping early also raises the chance of creating bacteria that are resistant to common antibiotics, forcing you to take more powerful antibiotics that may have more serious side effects. Worse yet, you can potentially spread these antibiotic-resistant bacteria to other people, expanding the population of hard-to-kill bacteria.

Some other things to remember about taking antibiotics:

  • Do not take more antibiotics than your doctor has prescribed.
  • Avoid keeping leftover antibiotics for another time.
  • Do not share antibiotics with other people. They may be infected by a different type of bacteria, which may lead to antibiotic resistance.
  • Familiarize yourself with common side effects of antibiotics.

If you need antibiotics or have questions about how antibiotics might affect your birth control, contact a doctor or book an appointment with PlushCare today.


PlushCare is dedicated to providing you with accurate and trustworthy health information.

NIH. Side Effects of Antibiotics. Accessed on January 29, 2021 at

Cleveland Clinic. Antibiotics. Accessed on January 29, 2021 at

CDC. Do antibiotics have side effects? Accessed on January 29, 2021 at

Most PlushCare articles are reviewed by M.D.s, Ph.Ds, N.P.s, nutritionists and other healthcare professionals. Click here to learn more and meet some of the professionals behind our blog. The PlushCare blog, or any linked materials are not intended and should not be construed as medical advice, nor is the information a substitute for professional medical expertise or treatment. For more information click here.

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