D-mannose is a kind of sugar that is related to glucose. D-mannose is used for preventing urinary tract infections (UTIs) and treating carbohydrate-deficient glycoprotein syndrome, an inherited metabolic disorder. How does it work? D-mannose might treat the deficiency caused by a genetic defect that causes abnormal breakdown and production of mannose. D-mannose might prevent certain kinds of bacteria from sticking to the walls of the urinary tract and causing infection.Treating a rare inherited disorder called carbohydrate-deficient glycoprotein syndrome type 1b. Some reports suggest that taking D-mannose supplements improves protein loss, liver function, low blood sugar, and blood clotting disorders in people with this condition. Preventing urinary tract infections (UTIs).