Selenium has a cell-protecting effect, and selenium supplementation therapy is mainly used to prevent and treat Keshan disease and macrosomia. Selenium supplementation does not cure diabetes; patients should also receive regular glucose-lowering treatment, including diet, exercise, and glucose-lowering drugs. Selenium is an essential component of glutathione peroxidase, which protects cell membranes by forming glutathione peroxidase, which breaks down lipid peroxides, removes free radicals generated by metabolism in the body, and prevents peroxidative damage to cell membranes. Selenium deficiency may cause lesions in the heart and joints, resulting in Creutzfeldt-Jakob disease and macrosomia. Selenium supplementation therapy is mainly used for coronary heart disease, myocarditis, Creutzfeldt-Jakob disease, and macrosomia. It is recommended that diabetic patients seek timely medical attention and receive regular treatment.