1,4-Anhydro-1,5-dihydroxy-empagliflozin-d4 is labelled 1,4-Anhydro-1,5-dihydroxy-empagliflozin (A637895), an impurity of Empagliflozin (E521510) which is a novel, potent and selective SGLT-2 inhibitor, improves glycaemic control and features of metabolic syndrome in diabetic rats.