A patient on a long-term high-dose vitamin E supplement is taking warfarin (an anticoagulant). Which evaluation best reflects the clinical concern and why?

• A. Vitamin E is water soluble and is rapidly excreted in urine so it will have no interaction with anticoagulants, eliminating any need for dose adjustment or clinical monitoring while taking warfarin.
• B. Because vitamin E is neither stored nor biologically active, the only real concern is that it might reduce vitamin K absorption, unexpectedly enhancing clotting and requiring an increase in warfarin dose to maintain anticoagulation.
• C. The patient should double vitamin E immediately to obtain antioxidant benefits that will always outweigh any interaction risk, without changing anticoagulant therapy or consulting a clinician because supplements are generally benign.
• D. High-dose vitamin E, as a fat-soluble vitamin stored in the body, can increase bleeding risk by interfering with anticoagulant therapy; therefore evaluating supplement dose and coordinating with the prescriber is necessary to reduce potential adverse interactions.

Answer: (D)