hello and thanks for the query.
 Coumadin is a medication that helps to prevent the formation of harmful blood clots, reducing your risk of a heart attack or stroke. Blood clots are formed through a series of chemical reactions, and vitamin K is an important component of these reactions. Warfarin works by limiting vitamin K activity in blood clotting, helping to slow down the formation of blood clots. 
If you are taking warfarin and thinking about supplementing your diet with protein shakes, you should carefully read the ingredients list to make sure it does not contain high amounts of vitamin K.
 Some protein shakes may also contain other dietary supplements that interact with warfarin, such as vitamin E, red clover, insositol hexaphosphate, ginger and ginkgo.
So carefully read the contents of your protein powder and if it has nothing of these,you can go ahead.
Best of luck.
Thanks

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