The 69-year-old actress and singer, daughter of Judy Garland, has checked into a treatment centre for help with substance abuse, according to reports.
A rep for Liza told People: "Liza Minnelli has valiantly battled substance abuse over the years and whenever she has needed to seek treatment she has done so.
"Considering she's doing so well, we expect that she'll be released shortly."
The entertainer had back surgery in September to correct an injury that had prevented her performing for most of the year. It also meant she couldn't attend friend Joan Rivers' funeral.
In a statement at the time, Liza said: "I am overwhelmed with the amount of love and caring that has been sent my way from all over the world."
Liza won an Oscar for her role in the musical Cabaret. She famously made a cameo in Sex and The City 2 in 2010, performing Beyonce's 'Single Ladies' at a wedding reception.
Her mother Judy Garland passed away in 1969 after a battle with drugs and alcohol.