The invention is directed to a blood bag system, comprising a closed, sterile bag of substantially transparent, bio-compatible material, defining upper and lower ends; an infusion port at the upper end of the bag; an outlet port at the lower end of the bag; an inlet port at the lower end of the bag; a hemo-concentrator having an inlet port and an outlet port; a pair of inlet tubes fluidly connected to the hemo-concentrator inlet port; and a pair of outlet tubes fluidly connected to the hemo-concentrator outlet port. One of the inlet tubes is fluidly connected to the outlet port of the bag, and one of the outlet tubes fluidly connected to the inlet port of the bag. The other of the inlet tubes and the other of the outlet tubes are temporarily sealed (e.g., clamped) to prevent flow therethrough. The bag, the one outlet tube, the hemo-concentrator, and the one inlet tube thus form a closed fluid circulation circuit by which a pump can recycle the blood through the hemo-concentrator. One aspect of the invention includes a hemo-concentrator system and a specially adapted tubing set, for easily and quickly converting the hemo-concentrator from conventional use to use in the blood recovery method. Other aspects of the invention are directed to the combination of tubing set with hemo-concentrator, and to the tubing set itself.