The blood system has a complex and fascinating cascade – one reaction triggers another in a course of approximately 15 different stages – that allows the blood to clot. This process is essential to prevent blood loss if any vessels are damaged externally or internally but it can become a problem if clotting occurs within a blood vessel. If this does occur, anticoagulants can be life-saving.

Anticoagulation therapy can only be initiated by a physician and should never be stopped without specialist approval. The most common anticoagulants are heparin, which works swiftly but is generally used only in the short term, and warfarin and coumarin, which are used for longer-term prescribing.