GCG and type 1 diabetes mellitus: Vitamin C has also been shown to improve the effects of other agents in a synergistic manner: for instance, when added to metformin, Vitamin C reduces cardiovascular diabetic complications [208], when added to glucagon-like peptide 1 (GLP–1), it further ameliorates endothelial function and reduces oxidative stress in Type 1 diabetic patients [209].