Will St. John’s Wort Affect Birth Control?

st-johns-wortHerbal remedies are very popular around the world. Many people prefer them to pharmaceuticals because they believe herbs can elicit positive results without serious side effects. However, plants produce a wide variety of chemicals at varying concentrations, and might have a number of effects on your body, both good and bad. Furthermore, since herbal supplements are not evaluated by the FDA for safety or effectiveness, consumers often don’t have ready access to evidence about herbal products. We can’t even be sure that they contain the ingredients that are listed on the label!


St. John’s wort might decrease the effectiveness of birth control pills, and might be unsafe during pregnancy.


One popular herb is St. John’s wort, or Hypericum perforatum. While the scientific evidence is mixed at best, many people believe that St. John’s wort can be used as an antidepressant. However, people often treat themselves with herbal supplements without guidance from a medical doctor or pharmacist — and without knowing whether or not these herbs are safe to use with any medications they might be taking.

Over the millennia, plants have evolved all sorts of powerful chemicals, such as toxins, to defend themselves against insects and other predators. For this reason, we can’t assume that plants only contain inert chemicals that won’t affect us or interact with the chemicals in other drugs and supplements we use. St. John’s wort, in fact, contains chemicals that interfere with other medications. It has been banned in France, and other countries require or are considering warning labels on St. John’s wort products so consumers can be aware of possible drug interactions.

According to the National Institutes of Health, birth control pills are in a “major” risk group for possible drug interactions with St. John’s wort. The “morning-after pill” (emergency contraception) could also be negatively affected by St. John’s wort. An important component of this herb is called hyperforin, a powerful chemical that causes the human body to metabolize certain drugs faster. Birth control pills are one of the many pharmaceuticals thought to be affected by St. John’s wort. One dose of a birth control pill is designed to last for around 24 hours, which is why you need to take your pill at the same time every day. However, if your body metabolizes the pill too quickly, there might not be enough of the drug in your body to last the full 24 hours.

When taken as directed, the birth control pill is more than 99 percent effective. It works by suppressing ovulation — if the ovaries don’t release eggs, there is nothing for a sperm to fertilize, making pregnancy impossible. Even if an egg does manage to squeak through, the Pill also thins the uterine lining, making it more difficult for a fertilized egg to implant in the womb. However, there is still a small risk for unintended pregnancy among users of oral contraceptives, especially when they don’t take their pills properly.

In the medical literature there are several published cases of unintended pregnancies occurring in people who were taking only oral contraceptives and St. John’s wort at the time of conception — but with only a handful of scattered reports, we can’t know whether this relationship is causal or coincidental. However, we do have much more evidence about the possible mechanisms by which St. John’s wort can interfere with birth control pills.

A review of the literature indicates that St. John’s wort might interfere with oral contraception and could cause breakthrough bleeding among people who take the pill. Furthermore, at least three small studies have provided evidence for this relationship:

  • A study of 18 women found that, while ovulation was not detected in subjects who were taking oral contraceptives and St. John’s wort simultaneously, breakthrough bleeding was more likely to occur. However, the authors pointed out that their subjects still had thinner uterine linings, meaning that even if fertilization did take place, the ovum would be less likely to implant in the uterus to cause a pregnancy.
  • A study of 12 women also found increased risk of breakthrough bleeding. The authors recommended that people taking oral contraceptives and St. John’s wort at the same time should back up their birth control with condoms.
  • A study of 16 women found that taking St. John’s wort and birth control pills simultaneously led to a 13 to 15 percent reduction in the the levels of contraceptive hormones circulating in the body. The authors also reported increased breakthrough bleeding, as well as evidence of “probable ovulation” and “possible ovulation.”

Unfortunately, these studies suffer from small sample sizes — although it’s interesting to note that the results point to the same conclusion, that St. John’s wort can interfere with the birth control pill, at the very least by possibly increasing risk for nuisance breakthrough bleeding. Larger studies have not yet been undertaken, however, making it difficult to say for sure how much of a risk St. John’s wort really poses to people taking oral contraceptives to prevent pregnancy.

St. John’s wort is “possibly unsafe” to take during pregnancy, and can have interactions with many other pharmaceuticals as well, highlighting just how potent the chemicals in this herb can be. Aside from birth control pills, St. John’s wort can interact with many other common medications, including:

  • antidepressants, such as Prozac, Paxil, and Zoloft
  • antihistamines, such as Claritin, Zyrtec, and Allegra
  • cyclosporine, which recipients of organ transplants sometimes use
  • dextromethorphan, a cough medicine
  • digoxin, a heart medication
  • immune-suppressing drugs, such as Humira
  • indinavir and possibly other HIV drugs
  • irinotecan and possibly other cancer drugs
  • triptan drugs, used to treat migraines
  • sedatives, including Ambien, Depakote, and Xanax
  • seizure-control drugs, such as phenytoin and phenobarbital
  • theophylline, which treats asthma, emphysema, and chronic bronchitis
  • warfarin and related anticoagulants

If you suffer from depression that you feel needs treatment, you can consult with a health-care provider to learn about your options. While herbal supplements are not regulated by the FDA and ingredients and dosages can vary from those listed on the label, if you wish to take St. John’s wort but worry about interactions with your birth control, you can learn about other options, such as the non-hormonal copper IUD. You can make an appointment at a Planned Parenthood health center to discuss which birth control method is right for you.

10 thoughts on “Will St. John’s Wort Affect Birth Control?

  1. Hi Anna, I was just curious if St. John’s wort affects the depo shot as well or just the pill. I’ve been wanting to give St. John’s wort a try but wasn’t sure if it would affect my birth control.

  2. Hey,
    Im on the contraceptive pill. I was taking st John’s wort for a couple of weeks. Now that I’ve stopped taking it, do you know how long it’ll take for the pill to be back to its full effectiveness??
    Thanks 🙂

    • Hi Elli! As you can see from this article, there really isn’t very much research on St. John’s wort and hormonal contraception at all. I looked to see if anyone had found the half-life of hyperforin (the active ingredient); this source says nine hours, this source says 24-48 hours. Sorry I took so long to reply to your question, but by now it should be out of your system! If you’re very concerned, you should use a backup method until you start your next cycle of pills.

  3. Hello! I just discovered the herbal tea I occasionally drink contains St. John’s Wort aerial parts. Should I be concerned about the effects it could have on the efficacy of my birth control? I take a monophasic pill (Levora), and I drink maybe 3 cups of this tea in a given week.

    • Hi Molly! I don’t think there is enough information out there to answer your question. As you can see from the article, there is very little published material on the interaction between St. John’s wort and hormonal birth control. Furthermore, it’s difficult to say what dose of hyperforin (the active ingredient) is in a product, given the variability in chemical concentration from plant to plant, as well as variables like how long you steep your tea, at what temperature, etc.

      A quick search (using medical subject heading terms “Hypericum” and “Contraceptives, Oral”) shows that there are only 15 scientific articles on St. John’s wort and birth control pills. They were all published between 2000 and 2009, which might indicate that interest in researching these interactions has waned. Of these, 13 are in English, and of these, only a few are actual studies of the interactions between St. John’s wort and birth control:

      * 3 are studies that do find that St. John’s wort had an effect on birth control pills (this study looks at low-dose pills; this study looks at a combined oral contraceptive; this study looks at low-dose pills and 300 mg St. John’s wort extract 2-3 times per day)
      * 1 is a study that did not find that a low dose of hyperforin had an effect on a low-dose birth control pill (here)
      * 1 is a study that did not find that St. John’s wort had an effect on the antiandrogenic effects of a low-dose birth control pill, but that’s not necessarily a study of whether it impacted the pill’s effectiveness in suppressing ovulation (here)
      * 2 were not studies but were reviews of other studies (here and here)
      * 1 was not a study but was a description of one woman who became pregnant while on the pill and taking daily doses up to 1700 mg of St. John’s wort (here)
      * 3 are letters to the editor
      * 1 is an article but not a study (here)
      * 1 is a study of whether pharmacists and health-food-store clerks in California tell customers that St. John’s wort can interfere with birth control

      That’s a quick and dirty search, and there could be more relevant studies out there, but this list provides a pretty good snapshot. As you can see, there really isn’t enough research out there to be able to answer more complicated questions like if a certain type of tea can interact with a particular brand of birth control. But the available evidence does show that there could be a risk, so people on hormonal birth control should be mindful about taking products with St. John’s wort.

  4. Hi I have the nexplanon implant and have been taking St. John’s wort for about 2 months now what are the percentages of me getting pregnant? St. John’s wort works wonders for me and I really don’t want to stop taking it!

    • Hi Alex! As you can see from the article, very little research has been done on the interaction between St. John’s wort and hormonal contraception. I can’t find any studies that have been conducted on possible interactions between St. John’s wort and Nexplanon, or its active ingredient, etonogestrel. WebMD has a neat tool for checking drug interactions. It does say that Nexplanon and St. John’s wort can interact to affect the implant’s effectiveness. You can read more about St. John’s wort here. It can be difficult to find useful information about herbal remedies, but this website is quite good.

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