Pharmacological and Parenteral TherapiesQuestion 832 of 2368

A client who takes warfarin asks about vitamin supplements. The nurse explains that which vitamin can interfere with the effectiveness of this medication?

  1. Vitamin K
  2. Vitamin B12
  3. Vitamin C
  4. Folic acid
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Correct answer: Vitamin K

Vitamin K is needed to make clotting factors. Excess vitamin K can reduce the effect of anticoagulants such as warfarin.

Source: Nursing Health Promotion (Open RN, Chippewa Valley Technical College, 2025), Healthy Diets: Essential Nutrients. Licensed under CC BY 4.0.

Practice the topic "Pharmacological and Parenteral Therapies"

Questions last reviewed: 18 October 2026