Answer is C (Accidental exogenous Insulin administration): Normal / Reduced levels of C- peptide in the presence of increased insulin suggest a diagnosis of exogenous insulin administration as the cause of hypoglycemia. Approach to a patient with Hypoglycemia and Increased Insulin levels: Role of C- peptide Assay Normally Endogemous Insulin is secreted from (3-cells of pancreas in the form of Pro-insulin This proinsulin is then broken down to Insulin and C- peptide such that for each molecule of endogenous insulin, one molecule of C-peptide is produced. C-peptide levels are thus increased whenever endogenous insulin is increased e.g. Insulinomas, Sulfonylureas, Autoimmune processes and in cases of Insulin resistance (type II DM).