Díaz Lab Testing Store › C-Peptide | Serum (Quest) Image 1 of 1 C-Peptide | Serum (Quest) $67.00 Measures pancreatic insulin production — differentiates Type 1 from Type 2 diabetes and evaluates beta cell function. Add To Cart Added! Measures pancreatic insulin production — differentiates Type 1 from Type 2 diabetes and evaluates beta cell function. Add-on | Interpretation for Individual Markers $17.00 Add Added!