INS and pancreatic insulinoma: As previously stated, the patient underwent an initial 72-hour glucose fasting test, and multiple serum glucose levels were determined to be 40 mg/dL (reference range: 70–125 mg/dL), with insulin and C-peptide levels appropriately albeit incompletely suppressed, with an insulin: glucose ratio of 0.18, findings felt to be inconsistent with an insulinoma.