Background: Hypoglycemia in Type 2 Diabetes Mellitus (T2DM) is typically drug-induced. Persistent hypoglycemia after discontinuation of all glucose-lowering agents is rare and suggests alternative etiologies such as insulinoma. Case Presentation: A 56-year-old female with T2DM presented with recurrent fasting hypoglycaemia despite cessation of all oral antidiabetic medications. Initial attribution to sulfonylurea uses delayed further investigation. Persistent hypoglycemia prompted endocrine evaluation revealing endogenous hyperinsulinemia. MRI identified a pancreatic tail lesion consistent with insulinoma. Conclusion: This case highlights diagnostic anchoring bias in diabetic patients and underscores the importance of evaluating persistent hypoglycemia beyond medication-related causes.