Thiamine plays a fundamental role in cellular metabolism. The classical syndrome caused by thiamine deficiency is beriberi, and its fulminant variant, once considered an uncommon finding, is now encountered among the critically ill.We present a case series of four critically ill non-septic non-alcoholic patients with severe lactic acidosis and refractory cardio-circulatory collapse caused by acute fulminant beriberi, which drastically responded to thiamine administration.In critical care settings, increased awareness of this life-threatening but reversible condition is a requirement, especially among patients receiving parenteral nutrition and those with unexplained recalcitrant lactic acidosis.