A blood transfusion is a way of adding blood to your body after an illness or injury. If your body is missing one or more of the components that make up healthy blood, a transfusion can help supply what your body is missing. Depending on how much blood you need, a transfusion can take between 1 and 4 hours. About 5 million Americans need a blood transfusion every year, and the procedure is usually safe. Your blood is made up of several different parts including red and white cells, plasma, and platelets. “Whole blood” refers to blood that has all of them. In some cases, you may need to have a transfusion that uses whole blood, but it’s more likely that you’ll need a specific component.

When you get a transfusion, the blood you’re given has to work with the type of blood you have (either A, B, AB, or O). Otherwise, antibodies in your own blood will attack it, and cause problems. That’s why blood banks screen for blood type, Rh-factor (positive or negative), as well as anything that can cause infection. About 40% of people have type O blood, which is safe to give almost anyone in a transfusion. If you have type O blood, you’re called a universal donor.If you have type AB blood, you can receive any type of blood and you’re called a universal recipient. If you have Rh-negative blood, you can only receive Rh-negative blood.