Glucose Transporter 1 (GLUT1) belongs to the major facilitator superfamily (MFS), one of the largest and most ubiquitous secondary transporter superfamilies. GLUT1, encoded by SLC2A1, mediates the basal-level cellular uptake of glucose into many tissues. GLUT1 contains 12 membrane-spanning domains with both the amino and carboxyl termini oriented intracellularly. In addition, a single extracellular N-linked glycosylation site is present.nGLUT1 is widely expressed, but it is most abundant in fibroblasts, erythrocytes, and endothelial cells with low levels of expression in muscle, liver, and adipose tissue.nInactivating mutations of GLUT1, resulting in compromised transport activities for glucose, are associated with diseases as a result of lack of energy supply to the brain. GLUT1 deficiency syndrome (also known as De Vivo syndrome) is characterized by a spectrum of symptoms including early-onset seizures, microcephaly and retarded development. In addition, elevated expression levels of GLUT1 have been observed in several cancer types, identifying GLUT1 as an important prognostic indicator for tumorigenesis.