Research
St John’s wort for Menopause: Evidence, Interactions and Cautions
St John’s wort is an ingredient used in menopause supplements marketed to women. Below is what it has actually been studied for, how strong that evidence is, the drug interactions and cautions on record, and the primary source our grade rests on — all drawn from the HerWellReport ingredient dataset.
Also sold as: Hypericum perforatum; hypericin; hyperforin
What the evidence says about St John's wort
NICE NG23 tells clinicians to advise people with a personal history of, or at high risk of, breast cancer that although there is some evidence St John's wort may help relieve vasomotor symptoms, there is uncertainty about appropriate dosage, persistence of effect, variation in the nature and potency of preparations, and potential serious interactions with other medicines including tamoxifen, anticoagulants and anticonvulsants. NCCIH says it is not consistently effective even for depression and should not replace conventional care. The interaction profile, not the efficacy, is the clinically decisive fact about this herb. The Menopause Society's 2023 statement does not assess it in its own right - it appears only as something sometimes combined with black cohosh - while the statement's blanket position is that over-the-counter supplements and herbal therapies are not recommended for hot flushes.
The grade "limited" means: limited — One or two small human trials, or trials for a closely related outcome. Grades are explained in full on our methodology page.
Read the primary source this grade rests on (opens in a new tab).
St John's wort drug interactions
- Tamoxifen
- warfarin and other anticoagulants
- anticonvulsants
- combined oral contraceptives
- ciclosporin
- tacrolimus
- digoxin
- oxycodone
- HIV antiretrovirals including indinavir
- irinotecan and other cancer chemotherapy
- SSRIs and other antidepressants (serotonin syndrome risk)
Who should be careful with St John's wort
- It induces CYP3A4, CYP1A and CYP2C9 and P-glycoprotein, so it lowers blood levels of many prescription medicines - have a pharmacist check every medicine you take before you start it
- contraceptive failure and transplant rejection have been reported
- never start or stop it without telling your prescriber, as levels of other drugs change both ways
- LiverTox rates its own liver injury risk as unlikely but notes it can increase the hepatotoxicity of other drugs through these interactions
Read more on HerWellReport
- Best Menopause Supplements: What Is Actually In Them
- O Positiv MENO Review: The Capsule and the Gummy Aren’t the Same Dose
- 65 Ingredients, None Proven: What Is Actually Inside the Supplements Sold to Women (2026)
This entry is generated from row "St John's wort" of the HerWellReport ingredient dataset (v2.1, updated 2026-09-23). The dataset is free to reuse under CC BY 4.0 — how to cite it. Ingredient evidence is not evidence for any finished product, and nothing here is medical advice.