Birth Control Herbs: What Works and What Interferes

No herb has been shown to work as reliable birth control, and some are toxic: pennyroyal oil has caused liver failure and death¹. The one supplement with consistent evidence of weakening the pill is St. John's wort, which raised breakthrough bleeding in 3 of the 4 studies in a systematic review².

Most other supplements have no human interaction data either way. Below, they are sorted into avoid, unproven and fine, with the trial behind each call.

No. What exists for contraceptive herbs is traditional-use records and animal experiments, not trials in women. A 2012 review catalogued 577 plant species traditionally used to regulate fertility in women, and 188 of them were recorded as contraceptives³. A 2015 review of the same literature closed by calling for more experimental work on mechanisms, not by confirming that any plant prevents pregnancy⁴.

What about mugwort?

Mugwort (Artemisia vulgaris) is the herb people search for most, and its evidence is in rats. An alcoholic extract caused irregular oestrous cycles and 80% anti-implantation activity in female rats⁵. A methanolic leaf extract cut implant formation by 100% and acted as an oestrogen in ovariectomised rats⁶. Neither study gives a failure rate or any result in a woman. We found no human data that mugwort tea prevents pregnancy, brings on a period or affects fertility, so there is nothing to build a contraceptive plan on.

Is pennyroyal tea a safe birth control tea?

No. Pennyroyal oil is dangerous. A case series of four ingestions included one death, and the authors' review of 18 earlier case reports found moderate to severe toxicity at 10 mL of oil or more¹. The toxin is pulegone, which damages the liver after glutathione stores run out⁷. The same review lists blue cohosh, rue and quinine among herbal abortifacients with significant illness and death⁷.

Home-brewed mint teas can contain pennyroyal by accident. In one report, two infants given such tea developed liver and brain injury, and one died⁸.

Barrier methods, the copper IUD, fertility awareness and permanent procedures all have measured failure rates. The CDC lists typical-use failure rates for each⁹:

• Copper IUD: 0.8%, and it can stay in place for up to 10 years.
• Male condom: 13%. The internal (female) condom is 21%.
• Diaphragm or sponge: 17%. The cervical cap is 22%.
• Spermicide: 21%.
• Fertility awareness methods: 2% to 23%, depending on the method and how consistently it is used.
• Breastfeeding (lactational amenorrhea method): works only while there are no periods after delivery, feeding is full or nearly full, and the baby is under 6 months old.
• Tubal surgery: 0.5%. Vasectomy: 0.15%.

For comparison, the CDC lists 7% for the combined pill, patch and ring, 4% for the injection and 0.1% for the implant⁹. Fertility awareness is the closest option to a natural method that has numbers behind it. Spermicides, which kill sperm, are products with a failure rate, not foods or herbs. No drink or supplement has data as a spermicide.

What can you take after unprotected sex?

Not an herb or a drink. The CDC lists a copper IUD inserted within 5 days, or emergency contraceptive pills taken up to 5 days afterward, and the sooner the pills are taken the better they work⁹. Some emergency pills are sold over the counter and some need a prescription⁹.

If you take St. John's wort, tell the pharmacist before using emergency pills. The prescription pill ulipristal (ella) carries an FDA label instruction to avoid combining it with St. John's wort, because CYP3A4 inducers sharply lower its blood levels¹⁰.

St. John's wort is the one with human trials. It speeds up CYP3A4, a liver enzyme that breaks down both ethinyl estradiol and the progestins in hormonal contraceptives². The CDC's 2024 guidance classes it as category 2 for combined pills, patches and rings, the progestin-only pill and the implant¹¹. It rates the copper IUD, the hormonal IUD and the injection as category 1, meaning no restriction¹¹.

The CDC's reasoning: studies raise concern that St. John's wort might lower effectiveness, including more breakthrough bleeding and ovulation, and the effect may depend on dose and preparation¹².

What did the trials find?

• Pfrunder 2003, 18 women: A low-dose pill (20 mcg ethinyl estradiol, 150 mcg desogestrel) plus 300 mg of extract two or three times a day. Bleeding between periods rose to 77% and 88%, against 35% on the pill alone. Exposure to the progestin fell by 43.9% and 41.7%. No ovulation was seen¹³.
• Hall 2003, 12 women: 300 mg three times a day for two cycles. Breakthrough bleeding occurred in 7 of 12 women, against 2 of 12 on the pill alone, and the half-life of ethinyl estradiol fell from 23.4 to 12.2 hours. Ovulation hormones were not significantly changed¹⁴.
• Murphy 2005, 16 women: 300 mg three times a day. Exposure to the contraceptive fell 13% to 15%, and bleeding, follicle growth and probable ovulation increased¹⁵.
• Will-Shahab 2009, 16 women: A low-hyperforin extract (250 mg twice a day for 14 days) did not change hormone levels. The ratios were within bioequivalence limits¹⁶.

The systematic review summed it up: limited evidence of ovulation and breakthrough bleeding raises concern about reduced effectiveness, and the hormone-level evidence suggests weak to moderate induction². Because the concentration of active ingredients varies between preparations, you cannot assume that your product is a low-risk one¹².

If you use St. John's wort for mood, do not stop a prescribed antidepressant on your own. Our guide to SSRIs and supplements covers what is safe to combine.

Probably not in a way anyone has measured. For these herbs, the data are lab results and general effects, not contraceptive trials. A 2020 review of herbs sold for weight, mood and immunity noted that their interactions with oestrogen-based pills are generally not known¹⁷.

• Ashwagandha: No trial has paired it with hormonal contraceptives. In human liver microsomes, extracts and their constituents showed no significant effect on CYP3A4¹⁸. A 2025 study in primary human liver cells found that a 70% ethanol root extract changed CYP3A4 expression and activity¹⁹. A 2026 meta-analysis of 23 trials in 1,706 adults found no change in estradiol in either sex, and testosterone rose in men but not in women²⁰. For its other uses, see ashwagandha benefits for women.
• Berberine: In healthy men, 300 mg three times a day for 2 weeks raised midazolam exposure by about 40%, which shows CYP3A4 inhibition²¹. The CDC notes that CYP3A4 inhibitors could in theory raise contraceptive hormone levels, not lower them¹². No study measured contraceptive hormones with berberine.
• Chasteberry and black cohosh: In test-tube assays, commercial chasteberry inhibited CYP3A4 with an IC50 of 0.3 mcg/mL. The authors say only studies in people can show whether that matters²².
• Fenugreek, creatine, magnesium and probiotics: Our searches found no study testing any of these with hormonal contraceptives. Absence of data is not proof of safety, but there is no signal to act on.

The sensible rule for the unproven group: if you take a hormonal method and start a new herb, watch for bleeding between periods. A pattern change is a prompt to ask a pharmacist, and to use a backup method until you know.

The effect runs the other way. In 29 people given a 6 mg dose, melatonin exposure was 4 to 5 times higher in pill users than in non-users, because the pill slows the enzyme (CYP1A2) that clears melatonin²³. So the pill changes your melatonin dose, not the reverse. Our guide to magnesium and melatonin together covers pairing it with other sleep supplements. We found no trial showing melatonin weakens the pill. If a usual dose leaves you groggy the next morning, ask your clinician about trying a lower one.

At 1 g a day, no. Early small studies had suggested that gram doses of vitamin C raise ethinyl estradiol levels. A randomized crossover study of 37 women on a 30 mcg ethinyl estradiol pill found no effect from 1 g of vitamin C on hormone exposure, and its authors said the interaction is unlikely to matter clinically²⁴. A follow-up in the same population found no effect on levonorgestrel levels or on the proteins that carry it²⁵. Vitamin C is not on the avoid list.

Slightly, and not for every nutrient. The evidence differs by vitamin:

• Vitamin B6: A review found population data that current low-dose pills may lower vitamin B6 status, which could matter if you stop the pill and become pregnant²⁶.
• Vitamin B12: The same review found that functional markers of B12 were not significantly affected²⁶. A separate study in young women found lower serum B12 in pill users, 172 versus 318 pmol/L, and called for further research²⁷.
• Folate: The review's authors concluded the available data do not show that currently used pills lower folate status²⁶.
• Iron: A WHO-sponsored study of 2,507 women found that hormonal contraceptive users generally had higher hemoglobin and ferritin than non-users²⁸. Pills reduce menstrual blood loss, which lowers the risk of anemia²⁹.

Taking the pill does not by itself call for routine supplements. Check iron status before supplementing it, and consider vitamin B6 or vitamin B12 only where blood tests or your diet point to low intake^{26, 27}.

Yes, and folic acid is advised either way. The NIH Office of Dietary Supplements recommends that women of childbearing age get 400 mcg a day of folic acid from supplements or fortified foods, in addition to dietary folate³⁰. The advice applies to anyone who could become pregnant, including people using contraception, since methods can fail⁹. We found no report that the vitamins in prenatal formulas weaken hormonal birth control. See folate for forms and doses.

Both can matter, in different ways, though neither has been tested with contraceptive pills.

• Biotin can distort hormone blood tests. We found no evidence that it weakens the pill. In 6 adults, 10 mg a day for 7 days caused interference in 9 of 23 (39%) biotin-based assays for thyroid and similar hormones, and some results read falsely high while others read falsely low³¹. Tell the lab before any hormone test.
• Activated charcoal binds drugs in the gut. In six volunteers, 50 g of charcoal swallowed right after a dose cut absorption of digoxin and phenytoin by about 98%. The effect was far smaller when charcoal came 1 hour later³². No pill study exists, so keeping charcoal many hours apart from your pill is a precaution inferred from this mechanism, not a tested rule.

Use this order of checks:

1. Name your method. A copper IUD, the hormonal IUD and the injection are category 1 for St. John's wort. Pills, patches, rings and the implant are not¹¹.
2. Look for St. John's wort. It hides in mood and sleep blends. If present, use a backup method or choose something else.
3. Check your other medicines. The CDC rates certain anticonvulsants and rifampin as category 3 for combined pills, patches and rings and for the progestin-only pill, and category 2 for the implant. They are a bigger concern than any supplement¹¹.
4. Track bleeding. New spotting after a new supplement is the signal to call a pharmacist.
5. Do not rely on herbs for protection. Pick a method from the CDC list above.

Pages that discuss women's hormone health, such as hormonal balance and women's health, cover what each supplement does for symptoms.

We searched PubMed through a research index for interaction trials, systematic reviews and pharmacokinetic studies on hormonal contraceptives with St. John's wort, vitamin C, melatonin, ashwagandha, berberine, fenugreek, creatine, magnesium, probiotics, biotin and herbs sold for hormones. We read the CDC's 2024 U.S. Medical Eligibility Criteria and its contraception overview, plus the NIH folate fact sheet. We prioritised systematic reviews and randomized trials in women, and we labelled laboratory and animal work as such. No trial tested most supplements with hormonal contraceptives, so several verdicts above rest on mechanism and absent evidence. Research completed 31 October 2026. This is general information, not medical advice.

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