INS and Hypoglycemia: To explore alternative causes of endogenous hypoglycemia, during her follow-up visits, simultaneous serum glucose concentration was 90 mg/dl (normal range 82-115 mg/dl) fasting Insulin and c-peptide levels were obtained, which were 4.1 uu/mL (normal range: 2.6-24.9 uu/mL) and 0.98 ng/mL (normal range: 0.80-3.85 ng/mL) respectively.