A patient on warfarin should avoid which of the following supplements?

A patient on warfarin should be cautious with supplements that can significantly affect blood coagulation. Black cohosh, while primarily used for menopausal symptoms, is not known to interact with warfarin in a way that affects coagulation.

The appropriate choice among the supplements would be garlic, as it has blood-thinning properties that can enhance the effects of warfarin and increase the risk of bleeding. Ginger also has antiplatelet effects, which could similarly affect blood clotting. Fish oil can impact bleeding risk as well if taken in high doses. Therefore, while black cohosh may not be ideal for all patients, it is not the supplement that poses the same level of concern as ginger, garlic, or fish oil when considering their effects on a patient's warfarin therapy.