The basketball player has been in a medically induced coma at Sunrise Hospital in Las Vegas since Tuesday, after being found unconscious at the Love Ranch brothel in Crystal, Nevada.
Insiders tell the site that Odom has "no brain activity" after a wild weekend that supposedly included sex, pills, and cocaine.
Another source said, "He is brain-dead. The tests showed no function.”
His organs, including his kidneys, are also failing.
Lamar's estranged wife Khloé Kardashian is making medical decisions on his behalf, and will likely be in charge of any life-support choices.
A source told People, "It's hard for Khloé. He is on his last leg," adding, "Everyone wanted to hope for the best, but nothing has changed. Now they are preparing for the worst."
There has also been speculation that Lamar's condition had stabilized after Khloé's family, including Kris and Kylie Jenner, and Kim and Kourtney Karadshian, were photographed leaving the hospital and boarding a private jet.