Fasting, postprandial and postprandial plus glucagon-stimulated plasma C-peptide levels in non-insulin-dependent diabetics and in control subjects.

We have studied fasting, postprandial and postprandial plus glucagon-stimulated plasma C-peptide levels in 149 non-insulin-dependent diabetics treated either with diet or oral drugs and in 101 non-diabetic control subjects. Diet-treated diabetics showed the highest fasting, postprandial and post-glucagon C-peptide levels in both sexes. In men, diabetics treated with oral drugs showed lower postprandial and glucagon-stimulated C-peptide levels than control subjects, while in women C-peptide levels in this group of diabetics were similar to those in control subjects. The distribution of individual plasma C-peptide levels was wide in non-insulin-dependent diabetics and control subjects and there was considerable overlapping in plasma C-peptide distribution for diabetics and control subjects. Fasting and post-glucagon plasma C-peptide levels in diabetics showed an inverse association to plasma glucose levels and a positive association to degree of obesity, but no association with the known duration of diabetes.