Justin Bieber has sent his ''prayers'' to Demi Lovato following her suspected overdose.

The 25-year-old singer was taken to hospital on Tuesday (24.07.18) after she allegedly suffered a heroin overdose, and her old pal Justin Bieber has admitted he was shocked by the news, as he believed the star was still sober.

Speaking to TMZ, the 24-year-old singer said: ''It's very sad. I haven't talked to her, but my prayers go out to her and her family for sure. I thought she was sober. That's terrible, right?''

Demi had been sober for six years at the start of this year, before she confessed last month in her new single 'Sober' that she had relapsed and broken her sobriety.

She sang in the track: ''Momma, I'm so sorry, I'm not sober anymore / And daddy, please forgive me for the drinks spilled on the floor.

''To the ones who never left me, we've been down this road before / I'm so sorry, I'm not sober anymore.''

The 'Sorry Not Sorry' hitmaker was reported on Tuesday night to be in a stable condition, and a few hours later it was claimed she had woken up and was making a recovery.

And Justin isn't the only star to send his thoughts to Demi in the wake of her suspected overdose either, as several of her friends took to social media shortly after the news broke.

Kehlani, who recently toured with the singer, wrote: ''sending huge recovery love to Demi. this is a very personal moment and respected delicately. all we can do is send our best wishes and love. addiction isn't simple nor easy. you're very loved, @ddlovato you'll beat this as you did before. (sic)''

Whilst Ellen Degeneres said: ''I love @DDLovato so much. It breaks my heart that she is going through this. She is a light in this world, and I am sending my love to her and her family. (sic)''

Other stars including Ariana Grande, Meghan Trainor, Maren Morris, Adam Lambert, and Emmy Rossum have also shown support for the 'Confident' singer.