He has to take this medicine for the rest of his life.
He'll have to take this medicine as long as he's alive.
ーHe has to take this medicine for the rest of his life.
「彼はこの薬を一生飲まなければいけない」
to take medicine で「薬を飲む・服用する」
the rest of one's life で「一生」
ーHe'll have to take this medicine as long as he's alive.
「彼は生きている限りこの先この薬を飲まないといけない」
as long as one is alive で「生きている限り」
ご参考まで!
He has to take this medicine every day for the rest of his life.
以下のように表現することができます。
He has to take this medicine every day for the rest of his life.
彼はこの薬を毎日、一生飲まなければなりません。
for the rest of his life で「彼の残りの人生ずっと」を英語で表現することができます。
お役に立てれば嬉しいです。
またいつでも質問してください。