Glycosylation (glycation) of proteins can cause cataractogenesis and cellular damage. Using a human red blood cells (RBC) model and two different methods, this study shows that the glycation of hemoglobin increases significantly in glutathione (GSH) deficient RBC exposed to high glucose levels in vitro. Hemoglobin glycation was assessed using both affinity and ion-exchange chromatography. GSH-deficiency was accomplished artificially by treating RBC with 1-chloro-2,4-dinitrobenzene (CDNB) as well as by using hereditary G6PD-deficient RBC. GSH replenishment by dithioerythritol (DTE) and dithiothreitol (DTT) significantly blocked the glycation of hemoglobin in GSH-deficient cells. There was a significant negative correlation between levels of GSH and glycated hemoglobin following treatment with DTE (r = -0.98, n = 5, p < .001) and DTT (r = -0.94, n = 5, p < .02). This demonstrates that GSH depletion can indeed increase glycation. Thus, GSH and G6PD-deficient cells are at a significantly greater risk for the glycation of proteins, which in turn can cause increased cellular damage.