The aim of the paper was to describe an unusual case of non lactic metabolic acidosis connected to hypophosphatemia and refractory to infusion of bicarbonate. A 37 year old man was admitted to Intensive Care Unit with a severe metabolic acidosis. On admission the arterial gas analysis showed non lactic metabolic acidosis (pH 7.17; base excess [BE] -20.3; lactic acid 0.8 mMol/L), with hypoxemia and critical hypocapnia. Despite therapy with bicarbonate the acidosis persisted. After 4 hours glucose phosphate was administered, although the phosphoremia was unknown. After phosphate supplementation an improvement of acidosis was observed. Our hypothesis is that in the kidney phosphate depletion caused impaired tubular reabsorption of bicarbonate, which led to a non lactic metabolic acidosis.