In facilitated diffusion, glucose movement follows a concentration gradient, that is, from a high glucose concentration to a lower one. For example, GLUT-1, GLUT -3, and GLUT-4 are primarily involved in glucose uptake from the blood. In contrast, GLUT-2, which is found in the liver and kidney, can either transport glucose into these cells when blood glucose levels are high, or transport glucose from these cells when blood glucose levels are low (for example, during fasting). [Note: GLUT-2 is also found in pancreatic β cells.] GLUT-5 is unusual in that it is the primary transporter for fructose (instead of glucose) in the small intestine and the testes.