The amount of insulin, the fuel-regulating peptide hormone which is formed from proinsulin in the beta cells of the pancreatic islets and which promotes the storage of glucose and the uptake of amino acids, increases protein and lipid synthesis, and inhibits lipolysis and gluconeogenesis, in a specified sample of serum, the clear liquid that separates from blood after it has clotted completely, i.e. blood plasma from which fibrinogen has been removed.