Abstract Introduction Decompensated diabetes (DM) precoma/comas states are major causes of hospital morbidity and mortality. These commonly include diabetic ketoacidosis (DKA), diabetic hyperglycemic hyperosmolar syndrome (DHHS), diabetic hypoglycemia coma (DHC) and diabetic lactic acidosis (DLA). Another less common decompensated DM precoma/coma state to be aware of is Diabetic ketoalkalosis (DKAL). We present two cases of DKAL due to severe hypercortisolemia (HCS) from ectopic Cushing's syndrome (ECS). Clinical cases; Case 1 was a 61 yr old AA woman with suboptimally managed type 2 DM who had been admitted for DKA 2 months before. She had marked hyperglycemia (blood glucose >500mg/dl) on repeated measures (RMs) and chronic diarrhea with tachypnea and altered mental status (AMS). She had heavy tobacco abuse and work up revealed a right lung mass biopsy of which showed a malignant neuroendocrine tumor presumed to be malignant bronchial carcinoid. Her initial lab tests showed marked metabolic alkalosis with severe hypokalemia and elevated anion gap, ketonemia and ketonuria. Presentation was typical of DKAL and subsequent work up showed ECS with serum cortisol > 110 (n; 4.3-22.4ug/dl) on RMs and serum ACTH 377-480 (n; 0/46pg/ml). Her metabolic derangements were corrected and HCS managed with mild impact using ketaconazole and octreotide but she died within a month of admission with intractable septic shock despite parenteral antimicrobials. Case 2 was a 46 yr old Hispanic man with heavy tobacco abuse admitted on account of AMS, tachypnea and upper abdominal pain. He had severe hyperglycemia (blood glucose >750mg/dl on RMs) though not known to have DM. HBA1c was > 15% indicating undiagnosed DM. Initial lab tests showed marked respiratory and metabolic alkalosis, marked hyponatremia, hypokalemia, hypo-osmolality but with ketonemia and ketonuria. Presentation was consistent with DKAL. Work up showed a left lung lesion with pleural effusion shown to be small cell carcinoma of the lung. He was also found to have profound HCS (serum cortisol >150ug/d; on RMs) confirmed due to ECS with serum ACTH, 1500-1800pg/ml. Metabolic derangements were corrected and he was started on ketoconazole and etomidate to correct HCS with little response. Elective bilateral adrenalectomy was planned but patient abruptly discharged himself AMA. He was readmitted ∼ 3 weeks later with a massive pulmonary embolism and acute respiratory failure from which he never recovered. He died ∼ 2 months later. Discussion + Conclusions DKAL is an uncommon but important potential acute presentation of decompensated DM. Early recognition and management requires close attention to the acid-base and electrolyte derangements that often accompany it. Among the many possible causes of DKAL severe HCS is an important possibility to be consider. Rapid diagnosis and institution of aggressive therapy of HCS is crucial as it often has high morbidity and mortality potential. Presentation: No date and time listed