To have a transfusion means to get blood or some part of it. The blood usually comes from another person, called a donor. Parts of the blood (blood products) are separated out so that a person getting the blood gets only the needed part. The rest of the blood products can then be given to others who need them. Blood and blood products are given (transfused) into the vein, through an IV (intravenous) line.

Blood transfusions save millions of lives in the United States every year. Recent estimates suggest that about half of Americans will need a blood transfusion at some point during their lives.

Transfusions of blood and blood products temporarily replace parts of the blood when a person's body can't make its own or has lost them from bleeding. People sometimes need transfusions after injuries or surgery, or if they have cancer or certain other diseases.

Here, we will describe blood and its parts (also called components) and why they are important. We will also explain how blood is donated and transfused and how that relates to people with cancer. For more precise information about how this works in your community, please contact your local hospital or blood donation center.