A blood product (or "blood-based product") is any component of blood which is collected from a donor for use in a blood transfusion. Blood transfusions can be used in massive blood loss due to trauma, or can be used to replace blood lost during surgery. Blood transfusions may also be used to treat a severe anaemia or thrombocytopenia caused by a blood disease. Early blood transfusions consisted of whole blood, but modern medical practice commonly uses only components of the blood, such as packed red blood cells, fresh frozen plasma or cryoprecipitate.