Warfarin has been used for more years than I have been around...The only real side iffect you should notice is that you will be less likely to throw a clot and suffer the consequences. Warfarin , when used properly and kept at a therapeutic level should change absolutely nothing else but your INR level...If your levels are correct you will struggle to notice any difference in bleeding times etc. from a cut on the finger or any other injury. I dont think I have ever heard it makes you tired. Its more likely your Beta Blocker doing that. Look it up on the website below to see if any other drug you are taking has a side effect with warfarin... here is the website with the best Warfarin info available...check here whenever you have heard of some silly myth and want to get the correct answer... http://www.warfarinfo.com/