Standard Breakfast Test: An Alternative to Glucagon Testing for C-Peptide Reserve?

Summary We measured C-peptide after glucagon and breakfast tests to compare the effectiveness of both tests in evaluating residual beta cell function in normal and diabetic subjects. A significantly higher C-peptide response was elicited after standard breakfast in patients with insulin-dependent diabetes mellitus of less than two years' evolution, ranging from 0.12 ± 0.07 to 0.83 ± 0.18 ng/ml (P < 0.05). In nonobese noninsulin-dependent diabetes mellitus the response ranged from 0.86 ± 0.02 to 1.89 ± 0.48 ng/ml (P < 0.0025); in obese NIDDM from 1.02 ± 0.37 to 1.55 ± 0.46 ng/ml (P < 0.05), and in normal subjects from 0.77 ± 0.23 to 2.11 ± 1.22 ng/ml (P < 0.0025). We conclude that the standard breakfast test is a useful and practical approach to the study of residual beta cell function.