Birth Control and St John's Wort: Why This Pair Fails

Medically reviewed by Dr Zainab Ajmal · Last reviewed September 2026 · Next review due September 2027 · MyStaq interaction record: oral-contraceptive-st-johns-wort

Why you are probably reading this

You have PCOS (now renamed PMOS). Low mood and anxiety are more common with PCOS, and St John's wort is the best-known herbal option for mild depression. You're also on a hormonal contraceptive, for pregnancy prevention, for cycle control, or to manage acne and hair growth. This is one of the few supplement-drug pairs where the answer is not "tell your prescriber." It's "not together."

What St John's wort does to your contraception

The active ingredient that matters here is hyperforin. It switches on CYP3A4, the liver enzyme that breaks down ethinyl estradiol and most progestins, and P-glycoprotein, a pump in the gut wall that pushes drugs back out before they're absorbed. Both effects reduce the amount of contraceptive hormone that reaches your blood and shorten how long it stays there [1], [2], [3].

Induction takes a week or two to build after you start the herb, and it takes about four weeks to fade after you stop, because the extra enzyme has to be cleared by the body [7].

What the trials found

Three controlled studies gave healthy women a low-dose pill with and without St John's wort:

• Twelve women, 300 mg three times daily: ethinyl estradiol's half-life fell by roughly half and norethindrone cleared faster. Breakthrough bleeding rose from 2 of 12 women to 7 of 12 [1].
• Eighteen women, 300 mg twice or three times daily: the progestin's exposure dropped by about 44 percent; breakthrough bleeding rose from 35 percent of women to 77 and 88 percent. No ovulation was detected in this group [2].
• Sixteen women: hormone exposure fell 13 to 15 percent, breakthrough bleeding rose, and the researchers saw follicle growth and "probable ovulation" in the St John's wort cycles [3].

A systematic review pooling these concluded that breakthrough bleeding is consistent across studies and that one study showed probable ovulation [4]. None was large enough to measure actual pregnancies, which is why the reassurance "no pregnancies were seen" means nothing: they weren't looking for them. Unintended pregnancies have been reported in women using both [2].

Two things the trials teach:

• Bleeding is a warning, not a safeguard. Spotting tells you the hormone level dropped. Its absence does not tell you it didn't.
• Response varies. In the first study, the women who bled were the ones whose enzyme induction was strongest [1]. You cannot know in advance which group you're in.

Which methods are affected

UK contraception guidance (FSRH), which has the most detailed advice on enzyme inducers and lists St John's wort among them, sorts methods into two groups [7], [8]:

Affected: the combined pill, patch and ring; the progestogen-only "mini-pill" (including drospirenone-only pills like Slynd); and the etonogestrel implant.

Not affected: the hormonal IUD, the copper IUD, and the DMPA injection. These work locally or at doses that induction doesn't undermine.

Emergency contraception is affected too. The copper IUD is the recommended option after unprotected sex during St John's wort use. If you use a levonorgestrel pill, UK guidance recommends a double dose (3 mg) with counselling that its effectiveness is uncertain; ulipristal (ella) is not recommended during, or for 28 days after, enzyme-inducer use [7], [8].

Why this matters more if you have PCOS

The pill is doing more than one job. In PCOS it's often prescribed for cycle regulation, to suppress androgen symptoms, and to protect the uterine lining. St John's wort weakens the hormone exposure behind all of those, so breakthrough bleeding and, plausibly, a return of acne or hair symptoms are on the table, not just pregnancy risk.

Spironolactone changes the stakes. Spironolactone is avoided in pregnancy because it can affect a developing baby, which is why prescribers pair it with reliable contraception, usually the pill [10]. St John's wort quietly removes that reliability. If you take spironolactone and the pill, this interaction is not a spotting nuisance; it's the one scenario the contraception was there to prevent.

Mood is a real problem with real treatments. Depression and anxiety are more common in PCOS, and the international guideline recommends screening for both [9]. St John's wort has evidence for mild depression, which is why people reach for it. But if you're on hormonal contraception the trade is a bad one, and if the alternative is an SSRI, that's a conversation worth having rather than a supplement worth risking. Note that St John's wort must not be combined with SSRIs either (serotonin syndrome), and that switching from one to the other needs a washout your prescriber will set.

"Low-hyperforin" products. One small study found a St John's wort extract with reduced hyperforin did not change contraceptive hormone levels [5]. That's a real finding, but US products rarely state hyperforin content; most are standardised to hypericin, which isn't the ingredient that matters. Unless the label states hyperforin content and a clinician confirms the product, treat every St John's wort product as an inducer.

What to actually do

If you're on the pill, patch, ring, mini-pill or implant and want to take St John's wort: don't start it. Talk to your prescriber about mood first. If St John's wort is still the choice, switch contraception to an IUD or the injection before you start.

If you're already taking both: use condoms from today, keep using them for 28 days after your last St John's wort dose, and decide with your prescriber which one to stop [7], [8]. If you'll be on the herb for under two months, UK guidance also suggests running the pill continuously or shortening the pill-free break to four days, to reduce the chance of ovulation [7].

If you've had unprotected sex during the overlap: treat it as a possible contraceptive failure. Copper IUD if you can get one; otherwise double-dose levonorgestrel, and a pregnancy test three weeks after [8].

If you're on the hormonal IUD, copper IUD or injection: this interaction doesn't apply to your contraception. St John's wort still interacts with many other medicines, so run your full list through the interaction checker.

What we do not recommend

• Taking St John's wort with any pill, patch, ring, mini-pill or implant. [1], [2], [3], [7]
• Relying on "no spotting" as proof you're protected. [1]
• Assuming a product is low-hyperforin because it's a low dose. [5]
• Ulipristal emergency contraception during or within four weeks of St John's wort. [8]
• Stopping the herb and assuming you're covered the next day. The effect fades over about four weeks [7].
• Combining St John's wort with an SSRI or SNRI.

How confident are we

When to talk to a clinician rather than read further

• You're taking both and have had sex without a condom in the last month
• You take spironolactone and the pill and want to start St John's wort
• You're on St John's wort for mood and want to switch to an antidepressant
• You're on the implant or a drospirenone-only pill and take, or recently took, St John's wort
• You think you might be pregnant

None of this replaces your doctor. It is meant to make the conversation with them faster and better.

Quick questions

Can I take St John's wort with birth control pills? No. St John's wort speeds up how your body clears the pill's hormones. In controlled trials most women had breakthrough bleeding, and one trial found signs of ovulation. UK contraception guidance treats the combination as risks outweighing benefits. The effect lasts about four weeks after you stop the herb.

Which birth control is safe with St John's wort? The hormonal IUD, the copper IUD and the DMPA injection are not affected. The pill, patch, ring, mini-pill and implant are.

I've been taking both. What now? Use condoms from today and for 28 days after your last dose of St John's wort. If you've had unprotected sex during the overlap, treat it as a possible contraceptive failure: ask about a copper IUD or double-dose levonorgestrel, and take a pregnancy test three weeks later.

Sources

1. Hall SD, Wang Z, Huang SM, et al. The interaction between St John's wort and an oral contraceptive. Clin Pharmacol Ther. 2003;74(6):525-535.
2. Pfrunder A, Schiesser M, Gerber S, Haschke M, Bitzer J, Drewe J. Interaction of St John's wort with low-dose oral contraceptive therapy: a randomized controlled trial. Br J Clin Pharmacol. 2003;56(6):683-690.
3. Murphy PA, Kern SE, Stanczyk FZ, Westhoff CL. Interaction of St. John's wort with oral contraceptives: effects on the pharmacokinetics of norethindrone and ethinyl estradiol, ovarian activity and breakthrough bleeding. Contraception. 2005;71(6):402-408.
4. Berry-Bibee EN, Kim MJ, Tepper NK, Riley HE, Curtis KM. Co-administration of St. John's wort and hormonal contraceptives: a systematic review. Contraception. 2016;94(6):668-677.
5. Will-Shahab L, Bauer S, Kunter U, Roots I, Brattström A. St John's wort extract (Ze 117) does not alter the pharmacokinetics of a low-dose oral contraceptive. Eur J Clin Pharmacol. 2009;65(3):287-294.
6. National Center for Complementary and Integrative Health. St. John's Wort.
7. Faculty of Sexual & Reproductive Healthcare, Clinical Effectiveness Unit. Drug Interactions with Hormonal Contraception. May 2022. Summarised with the enzyme-inducer table at: NHS Specialist Pharmacy Service, Using contraception with enzyme-inducing medicines.
8. Faculty of Sexual & Reproductive Healthcare. Emergency Contraception guideline (enzyme inducers: copper IUD preferred; levonorgestrel 3 mg; ulipristal not recommended within 28 days).
9. Teede HJ, Tay CT, Laven J, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome (screening for anxiety and depression; combined oral contraceptives). J Clin Endocrinol Metab. 2023;108(10):2447-2469.
10. U.S. Food and Drug Administration. ALDACTONE (spironolactone) prescribing information, 2025, Use in Specific Populations 8.1.
11. Combined oral contraceptive prescribing information, Drug Interactions section (drugs or herbal products that induce CYP3A4, including St. John's wort, may decrease effectiveness).

Related guides: Spironolactone and Potassium