A hexose is a monosaccharide, or simple sugar, containing six carbon atoms in the molecule (C6H12O6). The hexoses are by far the most abundant simple sugars and those most frequently found in food. Examples include the sugars glucose, fructose, and galactose.
Three aldohexoses, d-glucose, d-mannose, and d-galactose, are common in plants, either in the free state or as components of polysaccharide molecules. Other less important aldohexoses are d-idose, d-gulose, d-talose, d-allose, and d-altrose. The four ketohexoses are fructose, sorbose, allulose, and tagatose.
Almost all naturally-occurring polysaccharides are made up of hexose units.