Haemorrhage affects all patient groups. Coagulopathy (an abnormality of the clotting system) is closely interlinked with haemorrhage and can either place patients at risk of future bleeding or can exacerbate active ongoing bleeding. There are many causes of coagulopathy – both inherited and acquired. During major haemorrhage, the presence of an acquired coagulopathy increases the likelihood of a poor clinical outcome and a patient is more likely to require large transfusion volumes, critical care admission and is three to four times more likely to die. Other forms of coagulopathy, such as drug-induced coagulopathy (anticoagulant/anti-platelet use) or inherited bleeding disorders, both increase the severity of any active bleeding and place patients at higher risk for future bleeding when exposed to a haemostatic challenge, such as surgery. This risk must be recognized and mitigated. This review focuses on the clinical aspects of coagulation and haemorrhage in all these patient groups.