Which herb is known to increase bleeding risk?

• A. Garlic
• B. Vitamin C
• C. St. John’s wort
• D. Calcium

Answer: (A)

Some herbs can affect how blood clots by altering platelet function, which can raise bleeding risk. Garlic has compounds such as allicin and ajoene that inhibit platelet aggregation, slowing clot formation. This antiplatelet effect can prolong bleeding time and increase the chance of bleeding, especially for people taking anticoagulants or antiplatelet meds or who are about to have surgery. In contrast, vitamin C doesn’t have a meaningful impact on platelet function at typical doses, St. John’s wort mainly alters drug metabolism rather than bleeding directly, and calcium is a necessary cofactor in the coagulation process—supplements here aren’t known to raise bleeding risk. So garlic is the herb most commonly associated with increased bleeding risk. If a patient is undergoing surgery or on blood thinners, it’s wise to review garlic supplement use with a clinician.