Blood donation is a voluntary procedure. You agree to have blood drawn so that it can be given to someone who needs a blood transfusion. Millions of people need blood transfusions each year. Some may need blood during surgery. Others depend on it after an accident or because they have a disease that requires blood components. Blood donation makes all of this possible.There are several types of blood donation:Whole blood. This is the most common type of blood donation, during which approximately a pint of whole blood is donated. The blood is then separated into its components; red cells, plasma, platelets.Platelets. This type of donation uses a process called apheresis. During apheresis, the donor is hooked up to a machine that collects the platelets and some of the plasma, and then returns the rest of the blood to the donor.Plasma. Plasma may be collected simultaneously with a platelet donation, or it may be collected without collecting platelets during an apheresis donation.Double red cells. Double red cell donation is also done using apheresis. In this case, only the red cells are collected.