nil by mouth

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Senior Member
Hi, teachers.

I know 'nil' means zero. But I don't understand the phrase 'nil by mouth'. Could you help me with the explanation please?
I found it in a movie.

Here's the conversation.

A: Are you not eating?
B: Oh, I'm nil by mouth.
C: nil by brain
A: C!, I don't want any argument.
C: nil by common sense, nil by sensitivity...
A: C!

Thank you very much in advance.
  • Ann O'Rack

    Senior Member
    UK English
    "Nil by mouth" is a standard phrase used in hospitals to say a patient is not allowed to eat or drink anything, typically before an operation. It's a very well known phrase.

    In your example, C is playing with the phrase and saying that B is not only not eating or drinking anything, but isn't thinking, and has no common sense and no sensitivity. The other "nil" expressions are only useful in this specific context where they're a play on the "nil by mouth" that B already said, you can't use them as stand-alone expressions otherwise.


    Senior Member
    English - England
    'nil by mouth' is a sign placed above a hospital bed to indicate that the patient must not eat or drink. This is usually because they are about to have an operation under general anaesthetic. Picture

    The rest is a jokey conversation.

    Where did you find this conversation?
    Who is speaking?
    Where are they?

    (Posted at same time as the others)
    Last edited:


    Senior Member
    The name of the movie is Coronation Street. I forget the name of A, B, and C. But I remember that A is the father of B, and C. A who is the father asks B why she is not eating and B says "Oh, I'm nil by mouth." Then C (B's sister) interrupt saying "nil by brain" ... as you can see in the conversation above. I can't find the phrase 'nil by something' in my dictionary. I need your help.


    Moderato con anima (English Only)
    English (Singapore/UK), basic Chinese
    The name of the movie is Coronation Street.
    I know Coronation Street as a television soap opera.

    There is a wikipedia entry for the phrase here:
    Nil per os (alternatively nihil/non/nulla per os) (npo or NPO) is a medical instruction meaning to withhold oral food and fluids from a patient for various reasons. It is a Latin phrase whose usual English expansion is nothing by mouth (most literally, "nothing through the mouth"). Variants include nil by mouth (NBM).
    Nil by mouth​ is the standard BrE variant.


    Senior Member
    polszczyzna warszawska
    New question:


    Can "nil by mouth" also be used in the context of a blood test?

    For instance:
    1) I'm at a doctor's surgery. He sends me for a blood test to be done the next day and, among other things, says: Please come nil by mouth.
    2) Someone offers me a sandwitch for breakfast, but I've got a blood test scheduled for today; can I say: I have to be nil by mouth; I've got a blood test today.

    In both cases, it's the question of being "on an empty stomach". If "nil by mouth" isn't usually used in situations like the ones above, what would you suggest instead?

    Thank you,

    EDIT: The sample sentences I've given are more or less direct translations from my mother tongue (Polish).
    Last edited:


    Moderato con anima (English Only)
    English (Singapore/UK), basic Chinese
    I think those sentences sound strange to me. The primary use of 'nil by mouth' is in the hospital context, where a doctor or a nurse says, 'This patient is nil by mouth' and a sign is mounted around the bed (like in Biffo's picture).

    If you use it outside of the hospital context, it will be a kind of creative or quotative use of the phrase. For a blood test, the usual instruction is to fast for (say) 10 hours. If you say 'nil by mouth', your tone of voice should indicate that you are quoting the phrase out of the usual context in a creative fashion.
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