English Translation
Are you off your rocker?
It’s really odd translation for the sentence ‘Are you OK?’
Yes, although it’s idiomatic. The Greek might better be translated as ‘Have you lost your mind?’, ‘Are you crazy?’, etc. I suppose “Are you OK?” is a possibility with the right intonation and an eye roll . . .
Now, if you’re going from English to Greek, a plain ‘Είσαι καλά;’ or ‘Καλά είσαι;’ would be better.