The Los Angeles Fire Department received a medical call from a home along Laurel View Drive in Hollywood Hills on Tuesday shortly before 11:30 a.m.
Fire officials confirmed that a 25-year-old woman was transported to a local hospital. Police and fire officials have yet to confirm the identity of that woman.
But multiple sources told ABC News that Lovato is being treated at Cedars-Sinai Medical Center. Her condition was unknown.
Lovato has been outspoken about her battles with bipolar disorder and substance abuse.
In March, the singer retweeted a post of an interview she gave, during which she said she was six years sober.
In May, she tweeted that new music and lyrics would reveal the truth.
I’m just gonna let my lyrics say it all... new music coming very soon— Demi Lovato (@ddlovato) May 29, 2018
Just last month, Lovato released a new song called "Sober," which includes lyrics indicating she was not sober anymore.
According to Lovato's website, upcoming tour dates have been rescheduled.
Fellow musicians and celebrities, including Ariana Grande, Brad Paisley and Ellen DeGeneres have been reacting to the news on Twitter:
My friend @ddlovato is one of the kindest, most talented people I’ve ever met. Praying for her right now, addiction is a terrifying disease. There is no one more honest or brave than this woman.— Brad Paisley (@BradPaisley) July 24, 2018
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.— Ellen DeGeneres (@TheEllenShow) July 24, 2018