INS and Polydipsia: A 53-year-old male treated with pembrolizumab for esophageal carcinoma presented to the emergency department with shortness of breath, dry mouth, polyuria, and polydipsia. Blood results showed an elevation of blood glucose at 451 mg/dL (25.1 mmol/L), HbA1c at 7.2%, blood gas pH of 7.06 mmol/L, bicarbonate og 5 mmol/L, and a urinalysis positive for glucose and ketones. The patient was diagnosed with DKA and treated with IV hydration and insulin and recovered without complication.