C-peptide level in factitious hypoglycemia

Q: A 22-year-old college student residing in a dorm presented to the ED for the third time in a month with hypoglycemia without a history of diabetes. There is a suspicion of factitious hypoglycemia, as the roommate showed suspicion that he may be using his insulin. C-peptide level is sent. In the event of factitious hypoglycemia, the C-peptide level is supposed to be? select one

A) < 0.2 nmol/L

B) ≥0.2 nmol/L 

Answer A

Two tests that rule out factitious hypoglycemia or accidental or surreptitious insulin administration are

• C-peptide level less than 0.2 nmol/L, and
• plasma proinsulin level less than 5 pmol/L        

C-peptide level ≥0.2 nmol/L and plasma proinsulin ≥5 pmol/L need to be ruled out for an endogenous origin of hyperinsulinism, or other etiologies such as oral hypoglycemic agent-induced hypoglycemia, insulin autoimmune hypoglycemia, and nesidioblastosis/islet cell hypertrophy.

#endocrinology

References:

1. Bonnet-Serrano F, Devin-Genteuil C, Thomeret L, Laguillier-Morizot C, Leguy MC, Vaczlavik A, Bouys L, Zientek C, Bricaire L, Bessiène L, Guignat L, Libé R, Mosnier-Pudar H, Assié G, Groussin L, Guibourdenche J, Bertherat J. C-peptide level concomitant with hypoglycemia gives better performances than insulin for the diagnosis of endogenous hyperinsulinism: a single-center study of 159 fasting trials. Eur J Endocrinol. 2023 Feb 14;188(2):lvad012. doi: 10.1093/ejendo/lvad012. PMID: 36756737.

2. Awad DH, Gokarakonda SB, Ilahi M. Factitious Hypoglycemia. [Updated 2023 Sep 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK542310/