What is a blood transfusion?

A blood transfusion occurs when a person receives human blood through an intravenous (IV). Human blood is made up of many parts. Three main parts of blood may be transfused.

1. Red blood cells
   The red blood cell’s main job is to carry oxygen throughout the body (the “heme” part of the red blood cell does the carrying). All of the body's organs (especially the heart, lungs, brain, kidney) need oxygen to work properly.
   
   
2. Platelets
   Platelets are small sticky cells that the body needs to start blood clotting and to prevent or stop bleeding.
   
   
3. Plasma
   Plasma is mostly water but also has a number of proteins that help blood to clot.