off your head

off (one's) head

1. Crazy, insane, or eccentric. Often used humorously or sarcastically. Primarily heard in UK, Ireland. I think you're off your head for changing careers this late in life, but, hey, follow your dreams. He's off his head if he thinks he can get that engine fixed by this weekend. My auntie likes to let people think she's off her head, but she's actually incredibly clever and witty.
2. Severely intoxicated by alcohol or drugs. Primarily heard in UK, Ireland. No wonder he's failing—he's off his head every night! We all popped the pills and were off our heads by the time the concert started.
See also: head, off
Farlex Dictionary of Idioms.

off your head

BRITISH, INFORMAL or

out of your head

INFORMAL
1. If someone is off their head or out of their head, they are crazy. You must be off your head to live in this area. If he didn't kill anybody it was only by luck because he was out of his head and screaming like a maniac.
2. If someone is off their head or out of their head, they have taken so many drugs or drunk so much alcohol that they do not know what they are doing. Basically, this song sounds great when you're off your head on Ecstasy. These days I get out of my head on one glass of wine.
See also: head, off
Collins COBUILD Idioms Dictionary, 3rd ed.

off (or out of) your head

1 mad or crazy. 2 extremely drunk or severely under the influence of illegal drugs. informal
See also: head, off
Farlex Partner Idioms Dictionary

out of/off your ˈhead

(British English, informal)
1 crazy: Are you off your head?
2 not knowing what you are saying or doing because of the effects of alcohol or drugs: Don’t even try to have a proper conversation with him — he’s off his head.
See also: head, of, off, out
Farlex Partner Idioms Dictionary
See also:
  • (I) would if I could
  • this just in
  • believe it or not
  • bion
  • aforethought
  • are we having fun yet
  • Are we having fun yet?
  • be off (one's) trolley
  • be off (one's) nut
  • AWHFY
References in classic literature
"If you don't sleep to-night," he said, "you'll be off your head to-morrow."
Island of Doctor Moreau
were so off your head on drugs that you allowed the sisters to spend whatever they liked and yes I believe every word the Grillos have said, who after all only stole money."
Nigella 'off her head on drugs'
If you look at Wednesday's game you are off your head to think I could play the same team again." The sheer energy expended in United reaching the last four of Europe's premier club competition for the third season in a row means the players asked to do the bulk of the running will not be asked to put their bodies on the line again.
Fergie to ring the changes
If you look at Wednesday's game you are off your head to think I could play the same team again." The sheer energy expended in United reaching the last four of Europe's number one club competition for the third season in a row means the men asked to do the bulk of the running will not be asked to put their bodies on the line again.
Fergie to be a changing man for Cup
"HOT CHIP WILL BREAK your legs, snap off your head. Hot Chip will put you down, under the ground." This is a threat, coming from those thugs you see in the portraits above.
Hot chip
The campaign, Drug Driving, You'd Be Off Your Head, won the award for best international radio advert.
Award winner
With a star-studded cast including Charles Dance, Sean Bean and Emilia Fox, you'd have to be off your head not to watch this.
TV PEOPLE: BEST ON THE BOX; Heads you win
It's very, like, romantic, and then, "I love you, you love me, and then you broke my heart, so my father's going to chop off your head." [Laughs] There's always some heads rolling into canals.
The ballad of little Emmy
He told Campbell: "He was clearly drunk and you were clearly off your head.'
'I TURNED TO DRUGS WHEN MY PAL WAS MURDERED..'
Around 200 bus rears will be adorned with a special strapline saying Drug Driving - You'd be off your head.
Drug drivers in media campaign
Whatever is Polish for "off your heads", these two are it.
Finders keepers