lose all one’s marbles

lose (one's) marbles

To be or become mentally deficient, incompetent, or deranged; to become of unsound mind. My poor grandmother started losing her marbles after she had a stroke. I've been so sleep deprived lately that it feels like I've lost my marbles!

See also: lose, marble

lose (all) one’s marbles

tv. to become crazy. (see also have all one’s marbles.) Have you lost all your marbles?

See also: all, lose, marble