Demi Lovato has been rushed to hospital after being found unconscious at a house at the 8000 block of Laurel View Drive in the Hollywood Hills, Los Angeles, where her home is located.

Although nothing has yet been confirmed, TMZ have reported that they have been informed by law enforcement that she has suffered what appears to be a heroin overdose.

The 25-year-old singer-songwriter performed at the California Mid-State Fair on Sunday (July 22) with Iggy Azalea. She is set to play Atlantic City, N.J. this week on Thursday (July 26).

Last year, Lovato opened up about a new documentary called 'Beyond Silence', which follows three individuals with mental health problems and explores their varying experiences. 

The 'Give Your Heart A Break' sensation executive-produced the project. She explained that it's important to remind people that mental health is as valid and important as its physical equivalent. She said:

"You can hear in the documentary how different they are, but also how alike they are. It’s important that we get that message out there because mental health is so important — it’s just as important as physical health.”

She added: “I hope that this film will show people that there is nothing wrong with having a mental health condition. If you do have one, you are able to live well and thrive with a mental health condition, if you are able to speak up and be vocal about the things you are going through.”

Lovato marked 6 years of sobriety at her concert in Brooklyn, New York, in March this year.

She told the audience: "Yesterday, six years ago, I was drinking vodka out of a Sprite bottle at 9 in the morning, throwing up in the car, and I just remember thinking, 'This is no longer cute. This is no longer fun. And I'm just like my dad.' So I took a look at my life and I said, 'Something has to change, I've got to get sober' - so I did."

The music star also released a track last month called Sober from her Tell Me You Love Me album which revealed she was still struggling with her addictions. Earlier that month, the Cool For The Summer star cancelled her London show due to swollen vocal chords. 

Taking to Twitter, she said: "I write this through tears of frustration and sadness that I have to postpone my concert in London at the O2 tonight due to being very, very sick and with swollen vocal chords that were examined by an ENT (dr)."