Blood transfusion is a medical procedure involving the administration of donated blood or specific blood components to a recipient. It is primarily used to treat conditions such as severe anemia, significant blood loss following trauma, or certain hematologic disorders. To ensure safety and effectiveness, the process begins with extensive screening and crossmatching tests to determine compatibility between the donor and recipient. Blood can be fractionated into components, including red blood cells (which carry oxygen), plasma (containing clotting factors), and platelets (critical for clot formation). The transfusion replaces lacking elements, helping to restore normal physiological function and prevent circulatory collapse.