Massive transfusion with packed blood cells (PRBCs) or fresh frozen plasma (FFP) can result in dangerous complications including stroke, kidney failure, and cardiac arrest. A simple, bench top technique using a hemoconcentrator and dialysate solution is described to correct critical values of sodium, glucose, potassium, and osmolarity in PRBCs and FFP. Sodium, glucose, and osmolarity were corrected to normal or near normal values. Elevated potassium was reduced by 65%, but not completely normalized. A simple, bench top method for correcting dangerous abnormalities with PRBCs and FFP can be used to improve the safety of massive blood transfusion.