C-peptide analysis in diagnosis of factitial hypoglycemia in an insulin-dependent diabetic.

Factitial hypoglycemia from the surreptitious self-administration of insulin by an insulin-dependent diabetic, shown to have C-peptide secretory ability by glucose and tolbutamide stimulation tests, was strongly suspected by finding low plasma C-peptide immuno-reactivity and high plasma insulin levels during "spontaneous" hypoglycemia whereas during hyperglycemia the D-peptide immunoreacitivity was higher and the plasma insulin was lower.