How does insulin, via facilitated diffusion, alter glucose transport?

The main role of insulin is the management of glucose intake. The intake of glucose is dependent on two factors; the availability of GLUT4 glucose transporters and the facilitated diffusion mechanism. Insulin acts to ensure the availability of the GLUT4 glucose transporters in the plasma membrane. In the case of low insulin concentration, the GLUT4 will remain unused in  the cytoplasmic vesicles. To facilitate the intake of glucose in the cells, a mechanism of facilitated diffusion is used; and with the input of the GLUT 4 glucose transporters, more glucose is taken into the cell.

In the case of absence of insulin in the insulin receptors, the GLUT4 glucose transporters will remain in the cytoplasmic vesicles and thus the glucose will not be taken into the cells; as a result of this, the unused glucose will be taken back to the cytoplasm.