Absorption of monosaccharides in the small intestine is pivotal for caloric intake of mammalians and adjusted in accordance with food supply, food composition, and energy demand in diverse physiological and pathophysiological situations. In respect to caloric intake, D-glucose, D-galactose, and D-fructose are the most relevant monosaccharides. For absorption, monosaccharides must cross a layer of epithelial cells that are connected by tight junctions which do not allow permeation of monosaccharides. Because monosaccharides are hydrophilic, they cannot permeate cell membranes passively. Hence, for absorption of D-glucose, D-galactose, and D-fructose, transporters in the luminal brush border membrane and basolateral membrane of small intestinal epithelial cells are required. 

The use of oral rehydration solutions is common practice for treating and preventing dehydration during times of illness and/or sweat loss. Oral rehydration solutions leverage these sugar cotransporters due to other common water transporters being blocked by toxins where water absorption is temporarily suspended. The use of amino acid cotransporters is also of interest in the oral rehydration solution, specifically the SLC family.