Blood transfusion A blood transfusion is a common and safe procedure in which blood is given to you through an intravenous line in one of the body blood vessels. Blood transfusions are generally done to replace blood lost during the surgery or due to a serious injury. A transfusion also may be done if your body can't make blood circulation properly because of an illness. During a blood transfusion, a small needle is used to insert an IV line into one of your blood vessels. Through this line, you receive healthy blood to your body. Whole blood transfusion takes 1 to 4 hours time, depending on how much blood you need. Blood transfusions are very common. Each year, almost 5 million Americans need a blood transfusion. Most blood transfusions go well. Mild complications can occur. Very rarely, serious problems develop. The heart pumps blood through a network of arteries and also veins throughout the body. Blood has many vital jobs. It carries oxygen and other nutrients to your body's organs and tissues. Having a healthy supply of blood is essential to your overall health.