SummaryThe base excess value (BE, mmol/L), not standard base excess (SBE), correctly calculated including pH, pCO2 (mmHg), sO2 (%) and cHb (g/dl) is a diagnostic tool for several in vivo events, e.g., mortality after multiple trauma or shock, acidosis, bleeding, clotting, artificial ventilation. In everyday clinical practice a few microlitres of blood (arterial, mixed venous or venous) are sufficient for optimal diagnostics of any metabolic acidosis or alkalosis.The same applies to a therapeutic tool—then referred to as potential base excess (BEpot)—for several in vitro assessments, e.g., solutions for infusion, sodium bicarbonate, blood products, packed red blood cells, plasma. Thus, BE or BEpot has been a parameter with exceptional clinical significance since 2007.