INS and Polydipsia: A 57-year-old man with recurrent metastatic urothelial cancer was placed in a clinical trial for atezolizumab. By the fifth cycle of treatment, the patient developed polydipsia, weight loss, and fatigue. The patient’s blood work showed plasma glucose levels of 24 mmol/L (432 mg/dL), ketones of 6.3 mmol/L, elevated anion gap of 19.1, bicarbonate of 16.9 mmol/L, venous pH of 7.3, and a Hb1Ac of 7.5%. The patient was diagnosed with autoimmune diabetes secondary to a PD-L1 inhibitor and treated with insulin and intravenous fluids.