“…During storage of whole blood (WB) in CPDA (citrate–phosphate–dextrose–adenine) [1] and of red blood cells (RBCs) in SAGM (saline–adenine–glucose–mannitol) [1], there is a dramatic decrease in the concentration of 2,3‐diphosphoglycerate (2,3‐DPG) in the RBCs, resulting in a significantly lower delivery of oxygen to the tissues. During our previous study of a large number of blood or RBC samples, the level of 2,3‐DPG was found to decrease from 12–15 µmol/g of haemoglobin (Hb) on day 1 to very low values (for instance, 0·46–1·3 µmol/g of Hb) on day 28 [2,3]. 2,3‐DPG is produced during glycolysis, by the diphosphoglycerate shunt pathway [4], from 1,3‐diphosphoglycerate (1,3‐DPG) via the action of the enzyme 2,3‐DPG mutase.…”