We describe a 74-year-old woman who developed severe uncontrolled hyperglycemia after commencing alpelisib, a new oral PI3K inhibitor indicated for a metastatic breast cancer, despite taking oral anti-diabetic drugs, metformin and vildagliptin, combined with intravenous insulin infusion of up to 250 units/day. This evidence concerns the gene INS and Hyperglycemia.