PROBLEM TO BE SOLVED: To provide a means for finding an index of severity (survival rate) of a patient with a severe condition in which energy metabolism is disrupted and improving the severity. SOLUTION: It has been found that the severity of a critically ill patient can be predicted by using a change in blood branched chain amino acid concentration as an index, and further, it has been found that energy metabolism can be improved by administering leucine to a critically ill patient. As a result, it has become possible to provide a severity prediction method useful for emergency medical care and an energy metabolism improving agent. [Selection diagram] None【課題】本発明の課題は、エネルギー代謝が破綻した重症病態の患者の重症度（生存率）の指標を見出し、重症度を改善する手段を提供することである。【解決手段】血中分岐鎖アミノ酸濃度の経時的変化を指標とすることで、重症患者の重症度予測ができることを見出し、更に重症患者にロイシンの投与により、エネルギー代謝を改善できることを見出した。この結果、緊急医療に有用な重症度予測方法と、エネルギー代謝改善剤を提供できるようになった。【選択図】なし
