yeah wry and Jthomp are right.. according to Jehovah's Witnesses believe that Christians should not accept blood transfusions or donate or store their own blood for transfusion.
The following medical procedures are prohibited:
1. Transfusion of allogeneic whole blood, or of its constituents of red cells, white cells, platelets or plasma.
2. Transfusions of pre-operative self-donated (autologous) blood.