Longtime friend Tom McInerney told the Detroit Free Press he had been informed by Karras' wife, actress Susan Clark, the ex-Lions great is near death.
McInerney said the 77-year-old Karras had been hospitalized last week with swollen limbs due to complications from kidney failure and was told by Clark Monday his death could come within a matter of days.
Karras business associate Catherine Lincoln told the newspaper the ex-player was released from a Santa Monica, Calif., hospital over the weekend and has returned to his California home under hospice care.
"The entire Detroit Lions family is deeply saddened to learn of the news regarding the condition of one of our all-time greats, Alex Karras," Lions President Tom Lewand said in a statement.
Karras played with the Lions from 1958-1962 and 1964-1970, becoming one the game's most dominant defensive players.
After his retirement he turned to broadcasting and acting, including appearances in the movies "Blazing Saddles" and "Porky's" and TV shows such as "Webster" and "M*A*S*H."