The search strategy was based on a combination of Medical Subject Headings (MeSH) terms and keywords such as “type 2 diabetes mellitus,” “T2DM,” “metformin,” “iron deficiency anemia,” “anemia,” “oxidative stress,” “reactive oxygen species,” “malondialdehyde,” “superoxide dismutase,” “catalase,” “glutathione,” and “total antioxidant capacity.” Boolean operators, including “AND” and “OR,” were used to combine search terms appropriately. This evidence concerns the gene CAT and anemia.