Can Antibiotics Affect Your Birth Control?

By Terez Malka, MD
Medically reviewed checkmarkMedically reviewed
November 29, 2021

The whole point of birth control is to avoid pregnancy.

So you don’t want to do anything that could make your contraception less effective.

Yet certain medications can change how the body metabolizes hormonal birth control, including the pill, patch, and vaginal ring.

In these instances, unless you use another contraceptive, your risk of pregnancy increases. 

Many women wonder if antibiotics in particular interact with hormonal birth control.

After all, 125 million women were prescribed antibiotics in 2020 for bacterial infections like urinary tract infections (UTIs), sinus infections, and skin infections, and 14% of women between ages 15 and 49 take birth control pills. 

While you should always discuss your current medications with your healthcare provider, this article will help you understand if antibiotics affect your birth control.

I’ll discuss what the research says about taking antibiotics with birth control, how birth control works, and other medications that may interfere with birth control.

Can You Take Antibiotics with Birth Control?

The short answer is yes, you can take most antibiotics with most forms of birth control.

However, certain antibiotics make some hormonal contraceptives less effective, so be sure your healthcare provider knows if you take birth control pills or use a patch or vaginal ring.

What the research says

Research indicates that most antibiotics do not have an effect on oral contraceptives.

And while earlier data reported that, in extremely rare circumstances, amoxicillin, ampicillin, metronidazole, and tetracycline have caused contraceptive failure, most researchers consider these studies to be too small to be conclusive.

The bottom line: It’s safe to use most antibiotics with most birth control.

Rifampin

Rifampin (Rifadin, Rimactane) is the only antibiotic known to impact the effectiveness of birth control pills, patches, and rings.

Used to treat tuberculosis and other serious bacterial infections, rifampin can decrease hormone levels in the blood.

This means that hormonal birth control may not prevent ovulation, which can lead to unintended pregnancy.

Anyone who uses any of these forms of birth control should use a barrier method when taking rifampin to avoid unwanted pregnancy.

How Birth Control Pills Work

Birth control pills contain hormones that prevent pregnancy by:

  • Stopping or decreasing ovulation (the release of an egg from an ovary)
  • Thinning the endometrium (the lining of the uterus), which makes it harder for a fertilized egg to attach
  • Thickening cervical mucus, which prevents sperm from reaching the egg in the uterus

There are two different types of oral contraceptives that prevent pregnancy: combination pills and progestin-only pills.

For maximum effectiveness with either, take the pill at the same time every day.

Also be mindful that the hormones may not be absorbed properly if you vomit within two hours of taking them. 

Combination pills

Combination pills contain estrogen and progesterone and are the most common type of birth control.

Most of these pills come in 21- and 24-day regimens: You take “active” pills (ones that contain hormones) for 21 or 24 days.

Then you take “inactive” pills (hormone-free or “sugar” pills) or no pills for seven or four days.

This is referred to as cyclical dosing, and women have their period during this final week.

However, if a woman continually takes only active pills, menstruation will not occur.

Other birth control pills require consecutive daily consumption of active pills for 84 days plus six days of inactive pills.

During the final six days, a woman has her period.

Progestin-only pills (the mini pill)

The progestin-only pill is sometimes referred to as the “mini-pill”.

This pill is better for women who are breastfeeding or who have a history of blood clots and strokes, as it does not contain estrogen. 

Need antibiotics?

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Medications That May Interfere with Birth Control Pills

While antibiotics are extremely unlikely to disrupt the efficacy of birth control pills and other hormonal birth control, a myriad of other medications can.

Ask your healthcare provider if any new prescription medication may interact with your contraceptive.

HIV medications

Some medications used to treat HIV can interfere with hormonal birth control.

If you take any of the below, talk to your doctor to determine what type or types of birth control are best to use:

  • Darunavir (Prezista)
  • Efavirenz (Sustiva)
  • Lopinavir/ritonavir (Kaletra)
  • Nevirapine (Viramune)

Antifungal medications

Most antifungal medications don’t appear to affect hormonal birth control, however, griseofulvin (Gris-PEG) and ketoconazole (Extina, Nizoral, Xolegel) may.

Griseofulvin is used almost exclusively for a scalp and hair infection called tinea capitis, while ketoconazole is used to treat serious fungal infections. 

Anti-seizure medications

Certain anti-seizure medications such as the below can cause hormones in hormonal birth control to break down more quickly, rendering them less effective and increasing the risk of pregnancy. 

  • Carbamazepine (Carbatrol, Epitol, Equetro, Tegretol)
  • Phenytoin (Dilantin, Phenytek)
  • Felbamate (Felbatol)
  • Primidone (Mysoline)
  • Oxcarbazepine (Trileptal)
  • Phenobarbital (Luminal)
  • Topiramate (Topamax)

If you take any of these medications, doctors recommend using barrier contraceptives such as condoms and intrauterine devices (IUDs).

Birth control pills do not disrupt the effectiveness of anti-seizure medication.

Modafinil (Provigil)

Modafinil is used to treat the symptoms of sleep disorders such as sleep apnea and narcolepsy.

It also reduces the effectiveness of hormonal birth control.

Anyone using birth control pills, patches, or rings should consider other forms of contraception while taking this drug and for at least a month after ending the medication.

Herbal remedies

The main herbal remedy that can interfere with birth control is St John’s wort, which some people use to treat depression.

This supplement interacts with multiple drugs because it inhibits enzymes that help the body metabolize medication.

Symptoms that St John’s wort is affecting birth control include irregular monthly bleeding and breakthrough bleeding.

Anyone using St. John’s wort who is trying to prevent pregnancy should consider using a barrier method of contraception.

How K Health Can Help

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Frequently Asked Questions

Which antibiotics affect birth control?
While most antibiotics do not affect hormonal birth control, rifampin (Rifadin, Rimactane) can. It may decrease hormone levels in the blood, which could lead to ovulation and unintended pregnancy.
Do antibiotics mess with birth control?
Most antibiotics do not mess with birth control. However, rifampin (Rifadin, Rimactane) can reduce hormone levels in the blood and cause ovulation in a woman using hormonal birth control, including pills, patches, and vaginal rings.
How long after taking antibiotics does birth control work?
The only antibiotic known to affect birth control is rifampin (Rifadin, Rimactane). If you take rifampin, use an additional barrier method of contraception (such as a condom) for at least seven days after finishing the medication.
What cancels out birth control?
If you miss a dose of birth control or take St John’s wort, you may run the risk of pregnancy.

K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Terez Malka, MD

Dr. Terez Malka is a board-certified pediatrician and emergency medicine physician.

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