Demi Lovato is off the wagon in a big way.

The pop princess has been hospitalized for a heroin overdose, according to TMZ.

Our sources say Demi was transported from a home in the Hollywood Hills just before noon Tuesday, and is currently being treated. We do not know her condition.

Lovato had kicked her alcohol, cocaine and Oxycontin addiction about six years ago. However, she admitted in her recent track "Sober" that she has fallen back into bad habits.

Prayers.

Update: Lovato didn't OD on heroin. But she was given Narcan, which is used to counter the effects of opioids, on the way to the hospital.  Paramedics found her unconscious. Now she's "awake and responsive" and in stable condition.