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Oral contraceptives are one of the most common forms of birth control. The most prescribed type of birth control pill is a combined hormonal contraceptive that contains both estrogen and progestin hormones.

Like any medication, birth control pills don’t exist in a vacuum. If you’re taking other medications and supplements, they can affect how the pill works — and vice versa.

Read on to unpack some common concerns about interactions between the birth control pill and other medications.

Common Questions About Birth Control and Medication Interactions

The information below may help you avoid unwanted interferences between your medications.

How do medications affect birth control effectiveness?

Your body breaks down medications using enzymes in the liver, with a group of enzymes called cytochrome P450 (CYP) breaking down the majority of medicines. Certain drugs or supplements can change the speed at which these enzymes work.

If one medication speeds up these enzymes, it can impact other drugs you take. For instance, your body may then break down the hormones in the birth control pill too quickly.

Faster hormone breakdown might make the pill less effective. Medications that reduce birth control efficacy may increase your risk of pregnancy.

If a medication slows down these enzymes, birth control hormones may stay in your system longer. This can raise the levels of estrogen and progestin in your body. Drugs that interfere with contraceptives in this way may increase the risk of side effects, such as blood clots.

Do antibiotics interfere with birth control pills?

If you’ve ever searched “will antibiotics reduce the effectiveness of the pill?” online, you’ve likely encountered a lot of conflicting evidence. Antibiotics’ interaction with birth control has long been a topic of interest in medical research.

Antibiotics include a wide range of medications. It’s hard to prove or disprove an antibiotics’ effect on birth control. One important exception to this rule is rifampin, an antibiotic used to treat tuberculosis.

A 2023 study assessed people taking rifampin and another drug for tuberculosis. Researchers measured how they processed levonorgestrel, a type of progestin hormone popular in some birth control users.

The study found that people broke down levonorgestrel faster than usual, which may decrease the effectiveness of the hormone. If you’re taking rifampin, your provider may recommend a non-hormonal birth control method.

Which medications can make birth control less effective?

Certain medications can indeed interfere with birth control pills. Here are some medications that reduce birth control efficacy or interact with the pill in some way.

Lamotrigine and valproic acid

Often prescribed to prevent seizures or stabilize mood, lamotrigine and valproic acid can speed up how your body processes birth control hormones. This may make your birth control less effective.

Valproic acid — also known as valproate — is also associated with birth defects. People of childbearing age must be particularly cautious with this medication. If you’re taking valproate, talk with your doctor to ensure your contraceptive method is maximally effective.

Some experts recommend avoiding oral birth control if you’re taking lamotrigine and valproic acid. These drugs may even affect non-pill forms of hormonal contraception, such as the patch or the vaginal ring. Current evidence suggests that intrauterine devices (IUDs) may be the best alternative.

If you are taking these medications, talk with your provider. They can help you determine the best, most effective contraceptive method for you.

Clozapine

This medication is also used for certain mental health issues. But, unlike lamotrigine and valproic acid, clozapine slows down the metabolism of hormones. This could raise hormone levels and increase the risk of blood clots and other side effects.

Because of this, some experts advise a lower dose of clozapine if you’re taking oral birth control.

Enzyme-inducing anti-epileptic drugs

Carbamazepine is a common example of enzyme-inducing antiepileptic drugs (AEDs), which speed up the activity of CYP enzymes. This can reduce the effectiveness of oral birth control.

Clinical prescribing guidelines agree that if you’re taking these drugs, you should avoid the pill. Instead, experts may recommend methods like IUDs and perhaps the implant.

Migraine medications

An online search for “birth control pill effectiveness and medication” can turn up alarming results. Some might cause you to worry about topiramate, a common drug for migraines that is an enzyme-inducing AED, much like carbamazepine.

However, a 2023 cohort study of thousands of real patient data points confirmed what previous studies suggested. It found no increased pregnancy risk in people using low-dose topiramate (200 mg a day or less) with birth control pills.

While reassuring, check with your doctor about your specific risk. This is especially important if you’re on a higher dose of a medication like topiramate.

Can herbal supplements impact birth control?

Since they aren’t regulated the same way as pharmaceuticals, herbal supplements’ impact on birth control isn’t well-researched. They often reach the market without large clinical trials that could detect interactions.

However, studies of certain popular supplements have identified interactions with birth control pills. St. John’s Wort is a vital example. An herbal product often used for depressive symptoms, it speeds up CYP enzymes in your liver. This can lower your levels of birth control hormones and reduce contraceptive effectiveness.

A 2024 analysis found healthcare providers changed their birth control prescribing practices for people taking St. John’s Wort. This is why it’s crucial to tell your doctor about all the supplements you’re taking.

Many people assume supplements are safe because they’re natural. But the lack of regulation surrounding herbal supplements means this isn’t always the case. Even plant-based products can cause unexpected changes in hormone levels.

Can birth control pills affect other medications?

Hormonal contraception and medication you take for health issues can affect one another in both directions. Just as some drugs may change how birth control works, the pill can also change the behavior of other medications in your system.

Birth control pills increase the concentration of certain medications in the blodstream, which can raise the risk of side effects. For instance, birth control pills that contain estrogen may double one’s clozapine concentration. This can cause people to become overly sedated, as well as constipated.

Not all birth control pills are the same. Progestin-only pills, for example, don’t contain estrogen. They may not interact the same way as pills that combine estrogen and progestin hormones.