A method whereby initial Factor VIII activity normally present in blood collected into an anticoagulant which functions by chelating calcium is maintained for twenty-four or more hours without the necessity of the usual immediate freezing in either the whole blood or blood plasma. The method comprises mixing freshly collected blood or blood plasma prepared from that blood or freshly obtained blood plasma obtained by plasmapheresis, which blood or blood plasma has been collected into a calcium chelating anticoagulant, with a calcium-heparin solution in sufficient quantities to restore calcium to substantially normal physiological levels.
