Phrase(s): You’re out of your mind! [and] You’ve got to be out of your mind!
Inf. You must be crazy for saying or doing that! (Said to someone who has said or done something silly or stupid.) • Andy: go to the Amazon? You’re out of your mind! Jane: Maybe so, but doesn’t it sound like fun? • Mary: Come on, Jane. Let’s go swimming in the river. Jane: Look at that filthy water. Swim in it? You’ve got to be out of your mind!
McGrawhill's American Idioms And Phrasal Verbs