Over-the-counter Vitamin K1-containing Multivitamin Supplements Disrupt Warfarin Anticoagulation in Vitamin K1-depleted Patients. 

Most multivitamin supplements contain far less vitamin K(1) than thought to affect warfarin anticoagulation. Having described 3 patients with multivitamin-warfarin interactions, we hypothesized that vitamin K(1)-depleted patients are sensitive to even small increments. Therefore, we compared the eff …

Source: Over-the-counter Vitamin K1-containing Multivitamin Supplements Disrupt Warfarin Anticoagulation in Vitamin K1-depleted Patients. A Prospective, Controlled Trial – PubMed