Answer
Yes. It can reduce the effectiveness of hormonal contraception and increase the risk of breakthrough bleeding and unintended pregnancy.
Sources for this answer
- Care St John's Wort Low Mood Relief Tablets / UCalm St John's Wort Tablets — Current selected SmPCemc · Summary of Product Characteristics
- NHS Specialist Pharmacy ServiceNHS Specialist Pharmacy Service · NHS medicine guidance
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.