Anticoagulation is a fundamental component of medicine and is used to prevent and treat thromboembolic disorders by interfering with the blood coagulation process. The goal of anticoagulant therapy is to reduce the risk of pathological clot formation without causing excessive bleeding. Understanding the principles of anticoagulation requires an appreciation of the coagulation cascade and therefore how different anticoagulants work within this process. This is specifically relevant in urology in the context of acute bleeding and the safe pre-operative cessation of these drugs.