top of page


Updated: Aug 17, 2018

Vitamin K dependent clotting factors made in the liver include the clotting factors II, VII, IX and X as well as the anticoagulant proteins, protein C and protein S. Warfarin is a Vitamin-K antagonist and works to block its effects in the production of these clotting factors. Tests used to measure these clotting factors include the PT/INR which become prolonged with the use of warfarin. Warfarin therapy is closely monitored via the PT/INR tests to avoid toxicities such as the formation of clots/stroke etc.