The invention provides a method capable of detecting a trace amount of insulin contained in a sample.
The invention relates to an insulin detection method including: adding a sample to an electrode having an insulin binding protein immobilized on a surface of the electrode, the insulin binding protein specifically recognizing a site of insulin; and detecting an electrochemical change associated with formation of a complex of the insulin and the insulin binding protein. The insulin binding protein includes a first region that includes an α-CT segment of an insulin receptor and does not include a β subunit of the insulin receptor and a second region that includes an L1 domain of the insulin receptor and does not include the β subunit of the insulin receptor, and one of the first region and the second region is immobilized on the surface of the electrode.