US cyber attackers SwagSec, who had previously stated their intention to hack the singer's website, took information including names and email addresses on June 27, making them public this week.
Her record label Universal has contacted police and yesterday said: "The hackers took a content database dump from www.ladygaga.co.uk and a section of email, first name and last name records were accessed. There were no passwords or financial information taken.
"We take this very seriously and have put in place additional measures to protect personally identifiable information. All those affected have been advised."
Meanwhile, a source close to GaGa added: "She's upset and hopes police get to the bottom of how this was allowed to happen."
SwagSec previously hacked Amy Winhouse's official website.
Lady GaGa's official YouTube account was temporarily suspended this week amid copyright claims.
Watch the music video for 'The Edge Of Glory' below: