Emergency services responded to a call at Lovato's Hollywood Hills home on Tuesday, and transported the 25-year-old to a nearby hospital.
She apologises to her parents before singing in the chorus, "To the ones who never left me / We've been down this road before / I'm so sorry / I'm not sober anymore".
On Tuesday night Lovato was due to appear in an episode of Beat Shazam on US TV but network Fox announced they would pull the programme. "We have made a decision to replace the episode of Beat Shazam with another all-new episode".
Kehlani, who came out earlier this year and in April shared a kiss with Demi on stage, said she was "sending huge recovery love to Demi". She was scheduled to perform on Thursday (July 26) in Atlantic City as part of the city's beach concert series. Their occupants did not stop to speak to reporters.
A representative for the singer said Tuesday evening that Lovato was awake and recovering with her family. The two were then catapulted into the spotlight at the Disney Channel as teenagers, but their relationship fell on some hard times before Lovato entered rehab in 2010.
Demi has been known to openly talk about her addiction problems. Her debut album, the pop-rock "Don't Forget", released in 2008.
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Lovato, who has long battled substance abuse had been clean from cocaine for over six years.
The 25 year old was reportedly taken to a Los Angeles hospital shortly before midday following a suspected overdose and was issued with Narcan at the scene. "I had all the help in the world, but I didn't want it". "And I want her to know, thank you so much for being you, because I've seen all the great things she's done when I was on tour with her, talking to kids and telling her stories through her music and personally, backstage". Her entire tribe has rallied around her during the tough times, Lovato said. According to the dispatch call obtained by ET, Lovato was unconscious when paramedics arrived. "I wouldn't be here without them".
Selena wears a striped black and white dress in the picture, while Demi sports a bright red dress.
The star revealed to fans she recently relapsed in the lyrics of her new song, Sober, in June, apologising for letting her family and fans down. "I'm so sorry I'm not sober anymore/And I'm sorry for the fans I lost who watched me fall again/I wanna be a role model, but I'm only human", Lovato sang.