English Idiom – Lose (one’s) marbles

Meaning – Become crazy or insane. The idiom lose your marbles is used to describe someone who is acting in a confused or irrational manner, as if they have lost their mental faculties. It is often used as a way to describe someone who is behaving erratically or making poor decisions.

This expression can be used in a serious manner (“It’s so sad to see Grandpa losing his marbles in his old age.”) or it can be used jokingly (“You’ve bet your life savings on Chelsea to win the league? Have you lost your marbles?”)

More featured phrases to express some form of craziness or foolishness:


When could you use this idiom?

  • A relative is acting confused or irrationally after an illness.
  • Your friend has made a series of inexplicably bad decisions.
  • A colleague at work is making an extremely risky career move during a recession.
  • Your partner is so tired that they are behaving in an erratic manner.


  • “He’s been talking to himself a lot lately, I think he’s losing his marbles.”

In The News:

Is Britain about to lose its marbles?


  • Is there an idiom like this in your country?

What is an idiom?

An idiom is a word or phrase that is not taken literally.  An idiom is an expression that cannot be understood from the meanings of its individual words, but has a separate meaning of its own.