Sugar acids are monosaccharides that have had an -OH group oxidized to a carboxyl group.

Main classes of sugar acids include:

• Aldaric acids, in which the aldehyde functional group of an aldose is oxidized
• Aldonic acid, in which the terminal hydroxyl group of an aldose is oxidized
• Uronic acid, in which both ends of an aldose are oxidized

Examples of sugar acids include:

• Ascorbic acid
• Glucuronic acid