What is St. John's wort?
It's an herb with yellow flowers. It has traditionally been used for low mood, menopause and premenstrual syndrome (PMS).
In some countries, it's regulated as a drug ingredient and used together with black cohosh in menopause medications. In the US, it's sold freely as a supplement, so you need to be even more careful.
The biggest risk: it clashes with other medications
Your liver has enzymes that break down medications. St. John's wort strongly revs up these enzymes, so medications you take with it may break down too fast — or, in other cases, become stronger. That's why it's considered a top "culprit" in drug interactions.
| Medication | What can happen |
|---|---|
| Birth control pills | Birth control may become less effective |
| Antidepressants and other psychiatric/neurological medications | Effects may get stronger or change, causing drowsiness, headaches and more |
| Warfarin (a blood thinner) | Changes the level of the drug in your blood |
| Heart rhythm and heart medications (digoxin, etc.) | Effects may change |
| Immunosuppressants, anti-seizure drugs, antivirals, cancer drugs, antibiotics | Effects may change |
Other side effects: liver, alcohol, sleep, blood pressure
- Liver: It's known as an ingredient that can raise liver enzymes. The longer you take it, the more it may strain your liver.
- Alcohol: It has a calming effect, so combining it with alcohol can make you overly sluggish and drowsy. If you drink heavily 3 or more times a week, consider stopping.
- Sleep: Because it acts on the brain, it can actually disrupt your sleep.
- Blood pressure: Your blood pressure may drop and make you dizzy. If you feel dizzy after taking it, check your blood pressure.
Who should not take it
- □ You regularly take any prescription medication (especially birth control, antidepressants, warfarin or heart medication)
- □ You have liver problems or have been told your liver enzymes are high
- □ You drink often and heavily
- □ You have low blood pressure or often feel dizzy
If you take it anyway, don't take it long term — use it only when needed, for a short time. When choosing a menopause or PMS product, always check whether "St. John's Wort" is hidden in the ingredient list.
Medications and conditions to watch
- Caution Birth control pills — Birth control may become less effective
- Caution Antidepressants and other psychiatric/neurological medications — Effects may get stronger or change, causing drowsiness, headaches and more
- Caution Warfarin — Changes the level of the drug in your blood
- Caution Heart rhythm and cardiovascular medications (digoxin, etc.) — Affects liver enzymes, which may change how the medication works
- Caution Immunosuppressants, anti-seizure drugs (carbamazepine), antivirals, cancer drugs, antibiotics — Effects may change — don't take together
- Check Alcohol — Calming effects add up and can make you overly sluggish
Frequently asked questions
Can I take St. John's wort with birth control?
No. It can make your body break down birth control pills too fast, making them less effective.
Can I take St. John's wort with antidepressants?
No. The medication's effects may get stronger or change, causing side effects like drowsiness and headaches. If you take medication for your mood, talk to the doctor who prescribed it.
Can I take St. John's wort long term?
It's not recommended. It can strain your liver, so it's best taken only when needed, for a short time.
Is it okay if my menopause supplement contains St. John's wort?
If you don't take other medications, it may be okay for a short time. But if you take medications — or if you're buying it as a gift for a parent — it's safer to choose a product without it.
Can I drink alcohol while taking St. John's wort?
Avoid it. The calming effects add up and leave you overly sluggish, and the strain on your liver adds up too.
Related concerns
Last updated 2026-10-12