FABP4/FGF21 protein level ratio in blood (Ontology of Biological Attributes identifier OBA_2055431) can be described as follows. A compound attribute that is the ratio of amount of fatty acid-binding protein, adipocyte (human) in blood to amount of fibroblast growth factor 21 (human) in blood. Also known as: the ratio of amount of fatty acid-binding protein, adipocyte (human) in blood to amount of fibroblast growth factor 21 (human) in blood.