How to Take St. John's Wort Safely
Take 300 mg of St. John's wort three times daily with meals, but you must understand that this supplement can seriously interfere with many medications you may be taking, including birth control pills, and requires stopping at least 2 weeks before any surgery.
Dosing Instructions
- Take one 300 mg tablet or capsule three times per day
- Take each dose with a meal to improve absorption and reduce stomach upset
- Space doses evenly throughout the day (morning, midday, and evening)
- Swallow tablets whole with water
Critical Drug Interactions You Must Know About
St. John's wort is a powerful inducer of liver enzymes (specifically CYP3A4) that break down many medications, making them less effective 1. This is not a minor concern—it can cause serious problems:
Birth Control Pills
- St. John's wort reduces the effectiveness of oral contraceptives by 13-15% 2, 3
- This increases your risk of breakthrough bleeding and unintended pregnancy 2, 3
- You must use backup contraception (like condoms) if taking both 3
- Consider switching to a non-hormonal birth control method while using St. John's wort
Other Medications Affected
The supplement interferes with many drugs including 1:
- Blood thinners (warfarin)
- Antidepressants (risk of serotonin syndrome when combined)
- Immunosuppressants (cyclosporine, tacrolimus)
- Some cholesterol medications (pravastatin)
- Allergy medications (fexofenadine)
- Many others metabolized by the liver
Tell your doctor and pharmacist about ALL medications, supplements, and over-the-counter drugs you're taking before starting St. John's wort.
Sun Sensitivity Warning
St. John's wort contains hypericin, which makes your skin and eyes more sensitive to sunlight 4, 5. While studies at typical doses (up to 1800 mg daily) show minimal skin photosensitivity 5, there are important precautions:
Protect Your Skin and Eyes
- Wear sunscreen with high SPF when outdoors
- Wear protective clothing including long sleeves and a wide-brimmed hat
- Wear UV-blocking sunglasses to protect your eyes, as the supplement may contribute to early cataract formation 4
- Avoid tanning beds completely
- Limit time in direct, intense sunlight when possible
Common Side Effects
You may experience:
- Mild stomach upset (taking with food helps)
- Dizziness
- Dry mouth
- Fatigue
- Headache
- Increased sensitivity to sunlight
When to Seek Medical Help Immediately
Stop taking St. John's wort and contact your doctor or go to the emergency room if you experience:
- Signs of serotonin syndrome (if taking with antidepressants): confusion, rapid heart rate, high fever, excessive sweating, shaking, muscle stiffness, or agitation 1
- Severe sunburn or skin reactions after sun exposure
- Unusual bleeding or bruising (the supplement may reduce platelet aggregation) 1
- Symptoms suggesting medication failure (like breakthrough bleeding on birth control, worsening of conditions being treated by other medications)
- Severe mood changes or worsening depression
Before Surgery
You must stop St. John's wort at least 2 weeks before any planned surgery 1. The supplement:
- May increase bleeding risk
- Interferes with anesthesia and other surgical medications
- Affects how your body processes pain medications
Tell your surgeon and anesthesiologist that you've been taking St. John's wort, even if you've already stopped.
Important Considerations
- Do not start or stop this supplement without discussing it with your healthcare provider, especially if you take any prescription medications
- The strength and quality of St. John's wort products vary significantly between brands—look for products standardized to hyperforin content, ideally less than 1 mg hyperforin per day to minimize drug interactions 6
- Effects on medication levels can persist for 2 weeks after stopping St. John's wort 1
- If you're pregnant, nursing, or planning to become pregnant, consult your healthcare provider before use