To the Editor.
—In the March 1982 Archives (142:465-468), Santiago et al presented a well-organized, lucid review of adult fasting hypoglycemia. However, there is an error in his discussion. On page 467 he stated "low or undetectable levels of C peptide in plasma obtained during an episode of hypoglycemia with hyperinsulinemia are helpful aids in establishing a diagnosis of surreptitious insulin or oral hypoglycemic agent misuse."Two references1,2 are given for this statement; in neither one is data presented on patients taking oral hypoglycemic agents. However, in the discussion of reference 1, it is clearly stated that with oral hypoglycemic agents they "anticipate elevated levels" of C peptide "owing to stimulation of beta cell secretion. For this reason, this form of factitious hypoglycemia may be even more difficult to diagnose than insulin abuse, because the laboratory test may closely mimic the results with an insulinoma." This contradicts the statement