An ambulance was called to the set and Osbourne was taken away on a stretcher.
The celebrity news site reports, Osbourne was sitting in a chair, shooting the show in front of a full studio audience. Melissa Rivers was sitting next to her, filling in for Giuliana Rancic. Osbourne apparently turned to Rivers and said, "I don't feel good," and then fell out of the chair and started shaking. Melissa then turned Osbourne's head to help her. Someone from the audience, who was reportedly an emergency responder ran up and helped.
A few moments later, Osbourne came to and was alert. However, her team wanted her taken to the hospitalized for an evaluation. TMZ reports it's the first time Kelly has ever suffered a seizure.
The cause of Osbourne's episode is not known at this time. Johns Hopkins Medicine reports the exact cause of some seizures can be hard to pinpoint, many seizures can be classified as either provoked or unprovoked. A provoked seizure would include traumatic injuries to the head, whereas an unprovoked seizure would include seizures caused by, for example, a congenital defect.
For more information on seizures, click here.