A simple poly(dimethylsiloxane) (PDMS) microchip was employed to establish a relationship between red blood cell (RBC) antioxidant status and the ability of RBCs to interact with metal-activated C-peptide, a bio-active peptide reported to reduce some complications often associated with diabetes. It is known that the reduced form of glutathione (GSH) levels in the RBCs obtained from people with type 2 diabetes are lower in comparison to those RBCs obtained from healthy controls and accordingly, this correlation has the potential to implicate type 2 diabetes in high-risk individuals. A parallel channel microfluidic device for the quantification of GSH in age-based fractions, along with control and diabetic RBCs is described. Important to the fluorescence-based measurement is the simultaneous determination of the antioxidant without prior separation in either a six- or twelve-channel microchip. Here, we separated the RBCs using a density-based Percoll solution and quantitatively determined the concentration of GSH in younger, less dense RBCs to be increased more than 2-fold (336.7 +/- 29.6 amol/RBC) than older, more dense RBCs (137.0 +/- 25.3 amol/RBC). The ability of C-peptide to interact with the RBC membrane of the separated fractions was determined by immunoassay and it was found that the recovery of the C-peptide added to the younger RBCs increased by more than 40.6 +/- 12.7% above basal levels while with the older cells C-peptide increased by only 9.18 +/- 4.60%. These results suggest that GSH concentrations in the RBC may be useful in screening for resistance to C-peptide in vivo.