A Case of Post-Bariatric Hypoglycemia With Factitious Hypoglycemia

Diagnosing factitious insulin administration is challenging, especially in the rare instance where coexisting endogenous hypoglycemia is present. Delay in diagnosis results in higher morbidity and increases health care costs. This case highlights specific characteristics of both post-bariatric hypoglycemia (PBH) and factitious insulin use.

A 32-year-old woman with an extensive medical history including Roux-en-Y gastric bypass developed episodes of symptomatic hypoglycemia 8 months after bariatric surgery. She experienced postprandial hypoglycemia preceded by hyperglycemia, consistent with PBH, confirmed by a mixed meal tolerance test. During a 3-month period, she was hospitalized for hypoglycemia numerous times. During a 72-hour fast, she experienced hyperinsulinemic hypoglycemia due to surreptitious insulin use yet her c-peptide was not completely suppressed.

This is a unique case of concurrent factitious insulin use and PBH. Her c-peptide during fasting hypoglycemia was not suppressed as is expected with exogenous insulin use, yet her insulin to c-peptide ratio was elevated and her proinsulin level was low supporting surreptitious insulin administration.

This case exemplifies that surreptitious hypoglycemia should be considered in the differential diagnosis, especially when clinical features consistent with factitious disorder are present. Although c-peptide levels are typically <0.6 ng/mL (or <0.2 nmol/L) in insulin-induced hypoglycemia, this case highlights that this is not always present. Clinical presentation, along with proinsulin levels and the insulin to c-peptide ratio can provide additional insight into the underlying cause.