The molecule of the title keto carbasugar, C 7 H 10 O 4 , is formed by a cyclohexene skeleton with an envelope conformation, substituted by carbonyl, methyl and hydroxyl groups. The crystal structure is controlled mainly by a combination of strong O—H...O and weak C—H...O hydrogen bonds, forming nearly perpendicular chains running parallel to the [110] and [-110] directions. This perpendicularity is caused by a tetragonal pseudosymmetry influenced by the similarity between the a and b axes, the value of 90.9770 (10)° of the β angle and the action of a 2 1 screw axis, which transform each chain into its corresponding nearly orthogonal one.