Clinical Significance

C-Peptide levels, along with blood glucose and insulin levels are evaluated in patients with hypoglycemia to aid differential diagnosis and patient management. C-Peptide measurement has the advantage of not reacting with exogenous insulin which may interfere with the insulin assay. Factitious hypoglycemia due to surreptitious insulin injections may result in high insulin levels but low C-Peptide levels since exogenous insulin injections suppress beta cell activity.

Additionally, low C-Peptide levels along with high level of glutamic acid decarboxylase antibodies found in autoimmune diabetes are considered risk factors for continuing B-cell destruction in these patients. C-Peptide levels are increased in insulinomas. Measurement of C-Peptide has also been used to monitor patients’ response to islet-cell transplants.

In early studies of C-Peptide, it was considered biologically inactive, however, recent studies have shown that C-Peptide does exhibit bioactivity and measurement may be significant in type 1 diabetes. Studies have found that C-Peptide levels above 10 pmol/L in diabetic patients shows better metabolic control and can be associated with greater protection from diabetic complications such as nephropathy, neuropath, foot ulcers and retinopathy. Low C-Peptide levels were associated with severe hypoglycemia in diabetic patients