A system for washing red blood cells, comprising a separator configured to separate a quantity of blood into concentrated red blood cells having a hematocrit of at least 60% and a volume of 150-250 mL, and a supernatant component. The system comprises a flow controller configured to remove the supernatant component to provide an initial red blood cell concentrate combine 50-500 mL of an additive solution with the red blood cell concentrate to provide an intermediate red blood cell product intended for storage for 42 days or less, wherein the intermediate red blood cell product at the end of storage has an osmolarity value between 202-479 mOsm/L and wash the intermediate red blood cell product comprising the osmolarity value between 202-479 mOsm/L with a washing solution having an osmolarity value higher than that of the intermediate red blood cell product comprising the osmolarity value between 202-479 mOsm/L.
