A co-crystal composition comprised of Quercetin and at least one antidiabetic agent acts as a combination drug having unique physical properties and biological activity, which differ from both Quercetin in pure form and the at least one antidiabetic agent in pure form. The co-crystal composition may comprise quercetin and metformin. The co-crystals of quercetin and metformin may be prepared by grinding the compounds, and used in pharmaceutical compositions comprising these co-crystals. Co-crystal compositions of quercetin and Metformin may be used in combination with other anti-diabetic agents, including DPP-IV inhibitors.
