Video: Demi Lovato couldn't remember 'Sober' lyrics days before alleged overdose

Footage has emerged of Demi Lovato forgetting her own lyrics onstage just two days before an alleged drug overdose sent her to hospital.

The troubled 25-year-old pop star was reportedly discovered unconscious in her home by paramedics earlier this week, before being declared "awake and with family" by a representative.

Lovato can't remember the lyrics to 'Sober' in the video, the song in which she admits falling off the wagon after six years of sobriety.

"F**k, I forgot the words," she says in the clip, to cheers and laughter from the audience, before appearing to walk off stage.

The video was taken at the 2018 California Mid-State Fair on Sunday, July 22 (local time).

A concertgoer told Entertainment Tonight that Lovato didn't appear intoxicated during the incident.

"It was an emotional song. She seemed to be almost in tears," the witness said.

"As a fan, that made her seem more human. We all make mistakes. Even though she rehearses so many times, she makes mistakes. She is the first person to tell you we are all human and not perfect."

In the wake of her hospitalisation, Lovato has cancelled an upcoming concert in Atlantic City.

Newshub.