Glucose transporter type 1 (GLUT1 or SLC2A1) is a glucose transporter responsible for constitutive or basal glucose uptake. GLUT1 has a very broad substrate specificity such as pentoses and hexoses. GLUT1 is expressed at variable levels in many human tissues. Defects in GLUT1 are the cause of autosomal dominant GLUT1 deficiency syndrome, a blood-brain barrier glucose transport defect characterized by infantile seizures and delayed development. Defects in GLUT1 are also the cause of dystonia type 18 (DYT18), an exercise-induced paroxysmal dystonia/dyskinesia (muscle contraction disorders).