It's the latest medical problem for a family that has suffered a number of health challenges over the years.
TMZ says photos show Kelly Osbourne under a white sheet being rushed to the hospital after collapsing on the set. She was taping on set when she reportedly uttered, "I don't feel good," and then fell out of her chair.
The Hollywood Reporter says she was shaking. It did become widely reported that she had a seizure Overnight, Osbourne confirmed those suspicions tweeting a picture saying, "Thank U all 4 UR beautiful well wishes yes I did have a seizure they are just trying to figure out why"
Late Thursday, her publicist said she was staying overnight at an L.A. hospital for observation.
"They may be overly cautious in trying to hold someone because they are suspicious something's happening," said one doctor.
"Fashion Police" co-host Joan Rivers says she convinced Osbourne to go to the hospital.
"By the time she went to the hospital she was fine. She didn't want to go. I think I was the one who convinced her 'just go, don't be stupid," Rivers said.
The Osbourne family has faced some serious medical issues, most recently Kelly's brother Jack was diagnosed with multiple sclerosis, something their mother Sharon spoke about emotionally last summer on 'The Talk.'
"I want to thank everyone for all their and good will and love they've sent to us," SharonOsbourne said.
Sharon Osbourne has faced her own health scares; a decade ago she battled colon cancer, and within the last year, underwent a double mastectomy after learning she was predisposed to breast cancer.
"I had implants. And what happened was one of the implants was leaking, and it leaked into my stomach wall. And I had the cancer gene. And I'm like, see ya. Get them gone," she said.
Osbourne is the daughter of rocker Ozzy Osbourne and "The Talk" co-host Sharon Osbourne. She was profiled with her family on the MTV reality series "The Osbournes" and has appeared as a contestant on "Dancing with the Stars." She's currently a panelist on "Fashion Police" with Rivers, Giuliana Rancic and George Kotsiopoulos.
"She's fine," Rivers said in a video posted Thursday afternoon on the celebrity news site TMZ.com. "We just saw her."
The Associated Press contributed to this report.