Galactose exists in both open-chain and cyclic form. The open-chain form is an aldehyde (RCHO). Four isomers are cyclic, two of them with a pyranose (six-membered) ring and two with a furanose (five-membered) ring. Galactose is classified as a monosaccharide, an aldose, a hexose, and is a reducing sugar. One baby out of every 18,000 is born with a genetic defect of not being able to utilize galactose. Since galactose is in milk as part of lactose, it will build up in the blood and urine. Galactose, a member of a group of carbohydrates known as simple sugars (monosaccharides). It is usually found in nature combined with other sugars, as, for example, in lactose (milk sugar). Galactose is also found in complex carbohydrates (see polysaccharide) and in carbohydrate-containing lipids. Galactose (C6 H 12 O 6) is an important carbohydrate for cellular metabolism and one of the most abundant sugars in the human diet [37]. It is a reducing monosaccharide containing six carbon atoms, similar to glucose. Galactose is a simple sugar, a type of carbohydrate classified as a monosaccharide, meaning it is a single sugar unit. It acts as a fundamental building block for more complex carbohydrates. Galactose is a simple monosaccharide sugar naturally occurring in milk. When it’s chemically linked with glucose, it forms lactose, the principal sugar in milk and dairy foods. Galactose is important in early human development and plays a key role in our metabolism, even as adults. Learn what galactose is, its evidence-based medical uses, potential benefits, safe dosing in rare conditions, and why most people should avoid supplementation. Galactose is a simple sugar, which belongs to simple carbohydrates. Galactose is composed of the same elements as glucose, but has a different arrangement of atoms. Galactose is a naturally occurring monosaccharide that forms the disaccharide lactose when combined with glucose (another monosaccharide). Galactose is a fundamental simple sugar, chemically known as a monosaccharide. It is one of the three main dietary monosaccharides, alongside glucose and fructose, that the body absorbs directly for energy.