Although SGLT2-inhibitors are very useful drugs reducing blood glucose levels [75,79], unfortunately some T2DM patients taking SGLT2-inihibitors [79,83,91,92,93,94] show ketoacidosis via generation of ketone bodies such as β-hydroxybutyric acid due to extremely low glucose availability caused by SGLT2-inhibitors [75,79,82,84,95,96], resulting in severe insulin resistance. Here, SLC5A2 is linked to diabetes mellitus.