INS and metastatic melanoma: A 70-year patient with metastatic melanoma experienced diarrhea, vomiting, mucositis, and loss of appetite following the third treatment with pembrolizumab. The lab results showed a blood glucose of 51 mmol/L (918 mg/dL), pH of 6.99, ketonemia of 6.7 mmol/L, and lactate of 3.8 mmol/L. The patient was managed in the ICU with fluid therapy and IV insulin. The patient was discharged on insulin glargine and insulin aspart.