Kelly Osbourne is undergoing medical tests after suffering a seizure on the set of her TV show Fashion Police.
The 28-year-old star was rushed to hospital in an ambulance after collapsing during filming and is now being kept in for observation while doctors investigate what happened.
Kelly tweeted: "Thank U all 4 UR beautiful well wishes yes I did have a seizure they are just trying to figure out why?"
She also posted a picture of her distinctively tattooed arm lying on a hospital bed, with an intravenous tube attached.
Kelly was recording the latest episode of the style critics show alongside Joan and Melissa Rivers, who was standing in for usual panellist Giuliana Rancic.
According to TMZ.com, Kelly turned to Melissa and told her she didn't feel well, before she fell out of her chair shaking. There was a doctor in the audience who quickly came to her aid.
Kelly regained consciousness a few moments after the seizure, but her team wanted her to go to hospital for tests and supervision.
A spokesperson for the star told E!: "She was taken to a local hospital for further testing and is awake, alert and in stable condition."