While the potential utility of rCP as a biomarker for hypoglycaemia in individuals with diabetes has not been previously examined, previous research has shown that this test is highly correlated with mixed-meal-test-measured C-peptide [11] and has similar or superior utility to glucagon-stimulated C-peptide assessment for differentiating between type 1 and type 2 diabetes [34]. This evidence concerns the gene GCG and type 2 diabetes mellitus.