Lovato, 25, has spoken openly about cocaine and alcohol abuse. Representatives for Lovato did not respond to a request for comment but People magazine, quoting an unidentified source, reported she was "okay and stable."
TMZ, quoting law enforcement sources, reported that Lovato was found unconscious at her home and was treated with Narcan, an emergency treatment for suspected opioid and drug overdoses.
Los Angeles police said they had responded to a medical emergency on Tuesday involving a woman on the Hollywood Hills street where Lovato reportedly has a home, but declined to name the person.
Lovato released a song last month called "Sober" in which she sang, "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."
Lovato rose to fame on Disney Channel shows "Camp Rock" and "Sonny with a Chance" 10 years ago, and forged a pop career with hits like "Skyscraper" and "Sorry Not Sorry."
In a 2017 YouTube documentary, "Simply Complicated," Lovato spoke about years of substance abuse, eating disorders, and drinking, saying she first started using cocaine when she was 17.
She entered rehab at the age of 18, where she was diagnosed with bipolar disorder.
Lovato, who has some 69 million followers on Instagram, was in the midst of a U.S. tour and due to perform in Atlantic City, New Jersey, on Thursday.
Her hospitalization became the top trending item on Twitter on Tuesday, with fans and celebrities expressing concern and support.Country singer Brad Paisley tweeted, "Addiction is a terrible disease. There is no one more honest or brave than this woman."