ABSTRACT
Diabetic ketoacidosis is an acute complication of diabetic mellitus. The most common triggering factors are infection, insulin therapy omission and the onset of the disease, but if these are excluded, other less frequent etiologic factors must be ruled out. We report a case of 22-year-old woman with Graves' disease presented as diabetic ketoacidosis. She was diagnosed type 1 diabetes mellitus at 13 years old and continually has been treated with insulin therapy until now. She typically showed tachycardia at rest in spite of correction of metabolic acidosis. Hyperthyroidism worsens glycemic control in diabetic patients and may precipitate diabetic ketoacidosis. Hyperthyroidism always should be investigated in diabetic patients presenting diabetic ketoacidosis without obvious triggering factors.