Abstract: The present invention provides a method for determining 1,5-anhydroglucitol (1,5-AG) in a sample containing 1,5-AG, maltose and glucose, which comprises: converting maltose in the sample into glucose using an enzyme system capable of converting maltose into glucose; converting glucose into a compound which is not phosphorylated by 1,5-anhydroglucitol 6-phosphorylating enzyme system (AG-6P-ES) or dehydrogenated by the action of 1,5-anhydroglucitol-6-phosphate dehydrogenase (AG-6PDH), using an enzyme system capable of converting glucose into said compound; converting 1,5-AG into 1,5-anhydroglucitol-6-phosphate (1,5-AG-6P) using the AG-6P-ES; dehydrogenating the formed 1,5-AG-6P with AG-6PDH in the presence of an oxidized coenzyme; and determining the component formed or reduced by the dehydrogenation reaction. A reagent and a reagent kit useful in this method are also provided.