The 71-year-old Blue artist was reportedly rushed to the hospital on Tuesday afternoon and remains in intensive care.
Per TMZ, which was first to report Mitchell's medical crisis, a call was made from the singer-songwriter's Los Angeles home at around 2:30 p.m. to report an unconscious female, but that the patient was alert on the ambulance ride to the hospital.
There has been no comment yet from Mitchell's rep.
Mitchell, who was born in Canada but become one of the most iconic personalities to come out of the 1960s-era L.A. music scene, is an eight-time Grammy winnner, including the Recording Academy's Lifetime Achievement Award in 2002, and she was inducted into the Rock and Roll Hall of Fame in 1997. Her most recent studio album was 2007's Shine, but a number of compilations have been released since, including last year's four-disc Love Has Many Faces: A Quartet, A Ballet, Waiting to Be Danced.
The "Big Yellow Taxi" singer attended Clive Davis' annual pre-Grammys party back in February and she was honored last October at the UCLA Hammer Museum's 12th annual Gala in the Garden, which featured a performance by Sia.
"I think of myself as a painter first and a musician second," Mitchell said for the umpteenth time at the museum soiree.
Asked in 2010 about the common refrain that she's not covered more often because her songs are difficult to sing, Mitchell told the Los Angeles Times, "I'm a method actress in my songs, which is why it's hard to sing them. What I do is unusual: chordal movements that have never been used before, changing keys and modalities mid-song. But John [Kelly, creator of the tribute show Paved Paradise: The Art of Joni Mitchell] gets the spirit: You have to go to the brink of sadness but never fall into melodrama, then send in the clowns for a moment."
In the same interview, she explained her issue with her songs being considered "confessional."
"It's an ugly term—it's 'confessional' if you don't get it; if you do get it, you see yourself in the songs," Mitchell said. "I usually use 'I' as the narrator in my songs, but not all the 'I's' are me; they're characters. It's theater."