PROBLEM TO BE SOLVED: To provide a preventive or therapeutic agent for diabetes or obesity having glucokinase (GK) activating action.SOLUTION: A therapeutic agent comprises a crystal of a 2-pyridone compound represented by formula [1] (3-cyclopropyl-6-{(1R)-1-[4-(1,1-difluoroethyl)phenyl]-2-[(2R)-5-oxopyrrolidine-2-yl]ethyl}pyridine-2(1H)-one) or its tautomer, or a pharmacologically acceptable salt or solvate thereof, as an active ingredient.COPYRIGHT: (C)2016,JPO&INPIT【課題】グルコキナーゼ(GK)活性化作用を有する糖尿病又は肥満の予防又は治療薬の提供。【解決手段】式[1]で表される2-ピリドン化合物(3-シクロプロピル-6-{(1R)-1-[4-(1,1-ジフルオロエチル)フェニル]-2-[(2R)-5-オキソピロリジン-2-イル]エチル}ピリジン-2(1H)-オン)の結晶若しくはこの互変異性体、又は薬学的に許容される塩、又は溶媒和物を有効成分として含有する治療薬。【選択図】図1