Over a two-year period, the investigators will enroll patients diagnosed with Congenital Disorders of Glycosylation. The investigators propose to administer oral galactose supplementation for a period of 18 weeks in increasing dose to assess its effectiveness at normalizing glycosylation. Galactose will be given in a series of doses within the range of normal dietary intake of galactose over fixed time points. To assess the effects of oral galactose supplementation for each participant, changes in participant growth, as well as blood sugar levels, coagulation parameters and liver function (the primary clinical features of Congenital Disorders of Glycosylation) will be correlated with biomarkers derived from participant blood and urine samples obtained at key time points and then compared to standard normative ranges of data for each measure.