An object of the present invention is to provide a composition containing a pancreatic islet, a cell structure containing a pancreatic islet or a pancreatic islet cell, a pancreatic islet transplantation kit, a pancreatic islet transplantation treatment agent, and a hypoglycemic agent which improve at least one of glucose sensitivity or blood sugar level-reducing performance after transplantation, and to provide a composition containing a pancreatic islet, a kit containing a pancreatic islet, a pancreatic islet cell transplantation treatment agent, and a hypoglycemic agent which can improve glucose sensitivity. According to the present invention, a composition including A: a cell structure which contains a biocompatible macromolecular block and at least one kind of cell and in which a plurality of the above-described macromolecular blocks are arranged in gaps between a plurality of the above-described cells; and B: a pancreatic islet, and a composition containing a pancreatic islet; and a spheroid formed of at least one type of stem cell are provided.