This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
A patient presents with symptoms of hypoglycemia. Investigations reveal decreased blood glucose and increased insulin levels. C-peptide assay is done which shows normal levels of C-peptide. The most likely diagnosis is - 
Select and explain. 
A. Insulinoma, B. Accidental sulfonylurea ingestion, C. Accidental exogenous insulin administration, D. Accidental metformin ingestion
C: Accidental exogenous insulin administration
Answer: C: Accidental exogenous insulin administration 
Explanation: Answer is option 3- accidental exogenous insulin administration. Normal /reduced levels of C-peptide in the presence of increased insulin suggests a diagnosis of exogenous insulin administration as the cause of hypoglycemia. In patients with hypoglycemia and increased insulin, measure C-peptide - - - - - - increased C- peptide indicates increased endogenous insulin as in insulinoma, auto immune process, sulphonylurea ingestion. Normal or reduced C-peptide shows exogenous insulin administration. Ref Harrison 19 /2434