Fisher, 60, was hospitalized Friday in Los Angeles after going into cardiac arrest on a flight that originated in London.
Reynolds tweeted today:
While Reynolds used the term "stable," it is not an official medical status and Fisher's condition was not clear.
Fisher's brother, Todd, told ABC News on Friday that the actress was receiving care from "the very best" doctors.
“We just need to tell everybody to keep the prayers up because the doctors are doing everything they can for her right now,” he said. “She’s a real survivor and always has been and I would expect the best from this. That’s how we’re approaching it.”
Harrison Ford, who played Han Solo opposite Fisher's Princess Leia in "Star Wars," said in a statement: "I'm shocked and saddened to hear the news about my dear friend. Our thoughts are with Carrie, her family and friends."