Blood transfusion is an essential part of modern healthcare and can be lifesaving when used appropriately. In this podcast, Sophie Cook, The BMJ's clinical reviews editor, talks to Michael Murphy, consultant haematologist and professor of blood transfusion medicine at NHS Blood and Transplant at the John Radcliffe Hospital, Oxford, about best practice for the safety of patients receiving blood; including ways to reduce unnecessary transfusion, and the warning signs of an adverse reaction.