Defects in the coagulation system increase the risk of excessive bleeding during and after invasive dental procedures. This increased risk of bleeding is irrespective whether the coagulation disorder is inherited or acquired, for example by using anticoagulant medication. However, the cause of the coagulation disorder dictates preventive measures to be taken. Therefore, a careful medical history is crucial to identify and characterize patients with coagulation abnormalities. Recently, the insight in the mechanism of coagulation has increased considerably. This has resulted in specific procedures to adapt the level of coagulation required for specific invasive dental procedures. The dentist must discuss this temporary alteration of the coagulation level with the medical specialist of the patient.