mixed up with

mix (one) up with (someone)

1. To confuse or mistake one person for another. I always mix Kelly up with her younger sister—they look so much alike! Sorry, I think I'm mixing him up with someone from the accounting team.
2. To involve or embroil one with some other person, especially someone who is problematic, unpleasant, dangerous, etc. Often used in passive constructions. I heard Tom's gotten mixed up with some pretty shady people since he moved to New York City. I don't want you mixing Sarah up with any troublemakers, you hear me?
See also: mix, up

mix (something) up with (something else)

To confuse or mistake one thing for another. Here, take this jar instead—I mixed it up with the other one for a second there. Sorry, I think I mixed this file up with the one from last year's accounts.
See also: mix, up

mixed up with

1. Confused with or mistaken for someone else. I'm always getting mixed up with my sister Kelly because we look so alike. Sorry, I think I'm getting him mixed him up with someone from the accounting team.
2. Embroiled or entangled with some other person, especially someone who is problematic, unpleasant, dangerous, etc. I heard Tom's gotten mixed up with some pretty shady people since he moved to New York City. I don't want you mixing Sarah up with any troublemakers, you hear me?
3. In a romantic relationship with someone, especially someone who is unreliable, problematic, or otherwise unsuitable. Sarah's been mixed up with the drummer of some D-list band for the last month or so, but none of us see it going anywhere serious. My mother is so worried that I'll get mixed up with a girl who's a bad influence on me that she generally disapproves of anyone I date.
See also: mixed, up
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

*mixed up with (someone else)

involved with another person, possibly romantically. (*Typically: be ~; get ~.) I hear that Sam is mixed up with Sally. Who is Jerry mixed up with now?
See also: mixed, up
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
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References in classic literature ?
Mixed up with many striking, thoroughly dramatic physiognomies, it must be confessed that some of these portraits scarcely help at all to explain the power of the players to whom they belonged.
A WOMAN was given the wrong cancer treatment after her lab results were mixed up with another patient who had the same initials, an inquest heard.