Glucose transporter 3 (or GLUT3), also known as solute carrier family 2, facilitated glucose transporter member 3 (SLC2A3) is a protein that in humans is encoded by the SLC2A3 gene. GLUT3 facilitates the transport ofglucose across the plasma membranes of mammalian cells. GLUT3 is most known for its specific expression in neurons and has originally been designated as the neuronal GLUT. GLUT3 has been studied in other cell types with specific glucose requirements, including sperm, preimplantation embryos, circulating white blood cells and carcinoma cell lines. GLUT3 has both a higher affinity for glucose and at least a fivefold greater transport capacity than GLUT1, GLUT2 and GLUT4, which is particularly significant for its role in neuronal glucose transport, where ambient glucose levels are fivefold lower than in serum.