Used in biomedical research to measure rat fibroblast growth factor 21 (FGF-21) levels in biological samples such as serum, plasma, or cell culture supernatants. This ELISA kit enables researchers to study the role of FGF-21 in metabolic processes including glucose regulation, insulin sensitivity, and lipid metabolism. It is commonly applied in studies related to diabetes, obesity, and non-alcoholic fatty liver disease (NAFLD) in rodent models. The assay provides a quantitative, sensitive, and specific method to monitor changes in FGF-21 expression in response to pharmacological treatments or genetic modifications.