Stefani, 47, was admitted to Cedars-Sinai Medical Center in Los Angeles. She was scheduled to perform at the 21st Keep Memory Alive Power of Love gala at the MGM Grand Garden Arena in Las Vegas, but was forced to cancel her show due to doctor's orders, the outlet reports.
Jennifer Hudson reportedly filled in for the platinum blond beauty last minute. Prior to the show, she shared a video of herself getting ready to board a plane via Instagram.
"U call , I answer!" she captioned it. "Ms. Hudson is on the way!"
According to an attendee at the gala, Stefani filmed a brief video, in which she apologized for not being able to make it to the charity event. "I am so sorry that I cannot attend tonight, but I wanted to send a message of congratulations to Andre Agassi and my dear friend, Ronald Pearlman," she said in the clip.
"They did a stage announcement saying that they did have a special message from Gwen, because she wasn't able to attend," the eyewitness explained. "On stage, an MC did say that it was due to doctors' orders that she wasn't able to be there. They then played this really nice video of her. In the video, she was really enthusiastic and she talked about all the work that the organization does. She spoke really kindly about the institute and apologized that she couldn't be there. Towards the end of the video she said something along the lines of, 'I have a GRAMMY-winning surprise for you guys and you're going to love it! It was Jennifer Hudson."