Steroid induced diabetes mellitus, a complication due to corticosteroids, is commonly regarded as a form of type 2 diabetes mellitus. Hyperglycemic hyperosmolar syndrome, which requires relative insulin deficiency and concomitant elevation of counterregulatory hormones, such as glucagon, catecholamine, cortisol, and growth hormone, is acute a complication of type 2 diabetes mellitus. Here we report a case of hyperglycemic hyperosmolar syndrome induced by short-term steroid treatment in idiopathic thromobocytopenic purpura.