Atypical antipsychotics are very widely used for various psychiatric ailments because of their less extrapyramidal side effects. Various reports of disturbances in glucose metabolism in the form of new onset diabetes mellitus, exacerbation of preexisting diabetes mellitus, diabetic ketoacidosis, hyperosmolar nonketotic coma, acute pancreatitis, and increased adiposity have been reported. We present a case of new onset diabetic ketoacidosis in a patient without a history of glucose intolerance who was being treated with olanzapine for bipolar disorder. He presented in hyperglycemic, hyperosmolar, hyperketotic state with hyperkalemia, and peaked T waves on electrocardiogram. He was treated with vigorous intravenous hydration, insulin, and kaexylate which stabilized his metabolic profile. He was discontinued off of his olanzapine and started on resperidol for his bipolar disorder. Over the course of 6 months, the patient was discontinued off of his insulin and has been doing well on his follow-up appointments. This case highlights the necessity of close blood glucose monitoring of patient on atypical antipsychotic medications irrespective of their diabetic status.