Warfarin is the main oral anticoagulant used in the UK. Oral means it's taken by mouth. An anticoagulant is a medicine that stops blood clotting.

Clotting (thickening)is a complex process involving a number of substances called clotting factors.

Clotting factors are produced by the liver and help control bleeding. They work with cells that trigger the clotting process (platelets) to ensure blood clots effectively.

To produce some of the clotting factors, the liver needs a good supply of vitamin K.

Warfarin blocks one of the enzymes (proteins) that uses vitamin K to produce clotting factors. This disrupts the clotting process, making it take longer for the blood to clot.

This page covers:


Taking warfarin

Side effects of warfarin


Other useful information

Content supplied by the NHS Website

Medically Reviewed by a doctor on 26 Jan 2017