Option "C" ("Maintain a consistent intake of vitamin K-rich foods") is correct over "B" ("Avoid consuming grapefruit or grapefruit juice") because warfarin's effectiveness is directly impacted by the intake of vitamin K. Vitamin K plays a key role in blood clotting, and fluctuations in its consumption can affect how warfarin works. If a client suddenly increases or decreases their intake of vitamin K-rich foods (such as leafy green vegetables), it can interfere with the medication's ability to maintain proper blood thinning. Therefore, the instruction is to maintain a consistent intake of vitamin K, rather than increasing or decreasing it. On the other hand, grapefruit and grapefruit juice are more commonly associated with interactions with certain medications (like statins or some calcium channel blockers), but grapefruit does not have a significant interaction with warfarin. Hence, option "B" is not as relevant in this context as maintaining consistency with vitamin K intake is the key dietary consideration for clients on warfarin.
