A 24-year-old woman was treated with nivolumab for non-small cell lung cancer; two weeks after her second dose, she presented to the emergency department with abdominal pain, nausea, and weakness. Blood tests showed a glucose of 738 mg/dL (41 mmol/L), blood pH of 7.12, anion gap elevation of 30 mmol/L, and urine ketones above 80 mg/dL. She was treated in the ICU with IV fluids and insulin IV. Here, INS is linked to non-small cell lung carcinoma.