A 30-year-old woman is brought to the emergency department with sweating, tremor and confusion, blood glucose 38 mg/dL. She is a known diabetic. Plasma insulin is high and plasma C-peptide is undetectable. The most likely cause of her hypoglycemia is:
- A Sulfonylurea overdose
- B Insulinoma
- C Exogenous insulin administration ✓
- D Reactive hypoglycemia
Correct answer: C. Exogenous insulin administration
Explanation
B-peptide is cleaved from proinsulin in equimolar amounts with insulin during endogenous secretion, so high insulin with suppressed B-peptide indicates injected insulin. In sulfonylurea overdose and insulinoma both insulin and B-peptide are elevated together, which kills those distractors. This insulin-to-B-peptide dissociation is the standard biochemical test for factitious or iatrogenic insulin-induced hypoglycemia.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.