She is reportedly at the Timberline Knolls centre near Chicago, in the same rehab centre where Demi Lovato has received treatment in the past.
The 26-year-old said: "I'm a crusader for being yourself and loving yourself, but I've found it hard to practice. I'll be unavailable for the next 30 days, seeking treatment for my eating disorder... to learn to love myself again, exactly as I am."
On New Year's Day Kesha tweeted: "Cheers to this year being the best year ever. 2014 ton be the year of truth and freedom."
She later shared pictures of her getting a tattoo on her foot to celebrate the New Year.