Glucose transport in mammalian cells is dependent upon membrane-associated carrier proteins. Mammalian cells possess two types of glucose carriers (a) the Na⁺-glucose co-transporter and the (b) facilitative glucose transporter. The Na⁺-glucose co-transporter transports glucose against its concentration gradient by coupling its uptake with the uptake of Na⁺. It is largely expressed in epithelial cells of the small intestine and in kidney. The facilitative glucose carriers of the glucose transporters (GLUT) family accelerate the transport of glucose down its concentration gradient by facilitative diffusion. Members of the GLUT family are expressed in a tissue- and cell-specific manner and exhibit distinct kinetic and regulatory properties that reflect their specific functional roles.

It is clear that each glucose transporter operates most efficiently at different levels of blood glucose. For example, GLUT4 can swiftly reduce high levels of glucose in the post-parandial state. Elevated cell surface levels of the GLUT4 facilitate enhanced glucose uptake from the circulation and storage in fat and muscle. GLUT3 operates efficiently at low blood glucose concentrations in order to ensure constant supply of glucose to the brain when blood glucose levels are low. GLUT2, in its regulatory function, has an activity that is linear across a wide range of blood glucose concentrations and can provide an insulin demand signal to the pancreatic b-cells at various glucose levels.