Galactose, a monosaccharide sugar, is a key source of energy and is an important compound for early human development. Galactose is present in dairy products, the pectin of some fruits, vegetables, and some herbs. Children get most of their dietary galactose from milk. D-galactose is freely available in health food stores and is promoted for stimulating the immune system and improving gut motility in healthy individuals. Galactose as a part of food supplement participates in phase II of clinical trials for congenital disorders of glycosylation (CDG) patients. CDG is a group of more than 130 inborn errors of metabolism affecting N-linked, O-linked protein and lipid-linked glycosylation. In addition, monosaccharide is used in clinical trials phase I in patients with focal segmental glomerulosclerosis (FSGS), where the galactose lowers the level of a circulating factors that increase glomerular permeability to albumin in patients with resistant FSGS.