Supplements and anticoagulants.
Anticoagulants sit in a narrow therapeutic window. Push too far in either direction and the consequence is either a bleed or a clot. Warfarin is the most interaction-prone, but the direct oral anticoagulants (apixaban, rivaroxaban, dabigatran, edoxaban) also have documented supplement interactions.
Several supplements have INR-shifting evidence: curcumin, CoQ10, garlic extract, ginger, ginkgo, and high-dose fish oil push toward more anticoagulation. Vitamin K2 in higher doses pulls in the opposite direction and reduces warfarin's effect. St John’s Wort reduces warfarin levels via CYP induction and is a hard exclusion. Most of these are manageable with INR monitoring at initiation; we flag the ones that are not.
Something missing?
If a supplement or medication you take isn't in our autocomplete, tell us and we'll add it in the next quarterly update.