Bariatric surgery is a treatment increasingly used for morbid obesity and a significant number of patients undergoing this procedure will have diabetes. While bariatric surgery has been shown to be one of the most effective treatments for long term weight control, it has also been shown that it leads to improvements in comorbidities associated with obesity including type 2 diabetes. In fact one large series showed that over 80% of patients treated with gastric bypass procedures no longer required treatment for their diabetes. We report the case of a patient with insulin-treated type 2 diabetes who underwent gastric banding and 2 days post-operatively presented with severe diabetic ketoacidosis.