INS and metastatic melanoma: A 66-year-old female received nivolumab for metastatic melanoma with vaginal and cervical metastases. After six doses, they presented with nausea, vomiting, and weight loss. Blood tests showed a glucose of 531 mg/dL (29.5 mmol/L), HbA1c of 7.3%, pH of 7.29, bicarbonate levels of 12.2 mmol/L, and high anion gap of 23.8 mmol/L. The patient was diagnosed with DKA, received isotonic saline and continuous insulin infusion, and was discharged on a subcutaneous insulin regime.