Why is my blood still too thick after my dr upping my coumadin (warfarin) from 2.5 mg to 10 mg?

Everyone's different: Just follow your prothrombin time. It is not rocket science. The doctor will tell you when you are in therapeutic range. Some people take much larger doses of Coumadin (warfarin) to get adequately anti coagulated. It's all good.

Other issues: First, no such thing as "thick" or "thin" blood. If you need to have blood that does not make clots easily, we give Coumadin (warfarin) because it is "defective vitamin k". Your liver tries to use the Coumadin (warfarin) to make things necessary to make clots. Since the liver is getting defective vitamin k, it makes less things to make clots. If you eat a lot of k. Or have some other cause for clots, Coumadin (warfarin) fails.