Sodium/glucose cotransporter 1 (SLC5A1 aka SGLT1) actively and reversibly transports glucose (Glc) into cells by Na+ cotransport with a Na+ to glucose coupling ratio of 2:1. SLC5A1 is mainly expressed in the microvilli of intestine and kidney and responsible for the absorption of sugars. Overexpressed SLC5A1 has been found in various cancers, possibly playing a role in preventing autophagic cell death by maintaining intracellular glucose levels. Defects in SLC5A1 can cause congenital glucose/galactose malabsorption (GGM; MIM:606824), an autosomal recessive disorder manifesting itself in newborns characterised by severe, life-threatening diarrhea which is usually fatal unless glucose and galactose are removed from the diet. Mutations that cause GGM include D28N, D28G, Y191*, R379*, R135W, G100V and Q457R (Turk et al. 1994, Wright et al. 2002).