Blood component transfusion is a procedure undertaken by nurses across a range of clinical specialties. An understanding of why blood components are used, and the appropriate use of these components, is essential for all nurses involved in the transfusion process to ensure that transfusions are safe and effective, as well as to reduce the risk of preventable harm to patients. This article outlines guidance on appropriate transfusion in adult patients, focusing on the most commonly used components: red cells, platelets, fresh frozen plasma (FFP) and cryoprecipitate. It discusses what these components are and their use in adults, to reduce the risk of inappropriate transfusions. The aim of this article is to develop nurses’ knowledge of blood transfusion, to support them in improving clinical practice in this area.