Lovato, 25, was at her home in the Los Angeles area when emergency units were called just before noon Tuesday, News 6 sister station WPLG reported.
The report claims Lovato was unconscious when paramedics arrived and treated her with Narcan, an emergency treatment used in overdoses.
USA Today reports the Los Angeles Police Department confirmed a call was made at 11:37 a.m. PST for an overdose of a "female approximately 25 years of age," but did not confirm Lovato's identity.
Lovato's condition is unknown.
The singer entered rehab for depression at 18, and also admitted to using drugs and alcohol. Lovato said she was diagnosed with bipolar disorder during her time at rehab.
According to TMZ, Lovato had been sober for six years before today's incident.
Lovato tweeted earlier in the day that she would be appearing on the television show "Beat Shazam" at 8 p.m. Tuesday. There is no word on if the appearance was scheduled to be live or prerecorded.
i love u @ddlovato— Ariana Grande (@ArianaGrande) 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