The TV personality, 28, was hospitalized Thursday after fainting on the set of E!'s Fashion Police, her rep says, while on Thursday night Osbourne herself Tweeted a message to fans, along with a photo of her arm and its IV tube.
Said Osbourne: "Thank U all 4 UR beautiful well wishes yes I did have a seizure they are just trying to figure out why?"
Osbourne is undergoing "further testing and is awake, alert and in stable condition," the rep says. "She will be staying overnight for observation as a precautionary measure."
Mid-taping, Osbourne turned to fill-in host Melissa Rivers and said she didn't feel well, according to TMZ. She reportedly fell out of her chair right after and started shaking.
Osbourne's condition is unknown, but the show's fellow host Joan Rivers tells TMZ, "She is fine."
Entertainment Tonight earlier characterized it as a "seizure."
When it comes to health history, Osbourne has openly struggled with weight and substance abuse over the years.
Courtesy Kelly Osbourne