Publicist Charles Sherman says the 83-year-old has been touring the country performing a one-man show for more than three years. He has been portraying President Franklin Delano Roosevelt in "FDR."
Asner had to be taken off stage at the Marquette Pavilion in Gary, Ind. Tuesday night and taken by an ambulance to a hospital.
Sherman told ABC News that Asner is "resting comfortably" and is expected to be released later Wednesday.
Asner is best known for his roles in the TV shows, "The Mary Tyler Moore Show" and its spinoff "Lou Grant."