This is the title of a song originally sung by Frank Sinatra and now by Michael Buble. It means that you are very much in love with a person, although some people say it refers to injecting drugs "I've Got You Under My Skin" I've got you under my skin I've got you deep in the heart of me So deep in my heart, that you're really a part of me I've got you under my skin I've tried so not to give in I've said to myself this affair never gonna swing so well So why should I try to resist, when baby will I know damn well That I've got you under my skin I'd sacrifice anything come what might For the sake of having you near In spite of a warning voice that comes in the night And repeats, repeats in my ear Don't you know little fool, you'll never win Why not use your mentality, come on step up to reality But each time I do, just the thought of you Makes me stop before I begin 'Cause I've got you under my skin

There are two such phrases...get under somebody's skin=annoy somebody....have got somebody under someone's skin=be extremely attracted to someone....Pay attention to their difference,so I've got you under my skin=I'm attracted to you...I have left great impression upon you

To get under someone's skin means that you're annoying someone. Ex. "He just gets under my skin -- I really hope he doesn't come tonight." I've never heard the phrase used any other way, like to say "I've got you under my skin." I suppose that's just a playful use of language that turns a negative statement into something that sounds positive... I wouldn't just throw it around -- you would be misunderstood! ;)

That someone is so deep/strong in your heart as the blood in your system (blood is right under the skin right?) Hope you get the meaning. Similar to other one: "I love you to the bone" :)

In this context (a song I guess ?) The guy tells her he loves her , has feelings for her ,he got her deep in his heart and thinking of her etc.