Table 2.

Indications for c-peptide measurement

Diagnostic

To define T1DM

Criteria for acceptance for CSII

To determine whether T1DM or T2DM

Diagnostic test for MODY

Diagnostic test for LADA, in addition to antibody testing

Prognostic

Marker of duration of diabetes

Lower levels are associated with microvascular complication risk in T1DM

Associated with glycemic variability/HbA1C level

Lower levels are associated with greater hypoglycemia risk

Therapeutic response

Lower baseline levels associated with increased need for insulin

Lower baseline levels associated with shorter time to insulin treatment

Higher levels present in patients who respond to metformin and glibenclamide in combination

Higher levels associated with response to thiazolidinediones

Correlates with reduction in HbA1C following initiation of GLP-1 agonist therapy

CSII continuous subcutaneous insulin infusion, MODY maturity-onset diabetes of the young, LADA latent autoimmune diabetes of adults