The gossip website said Saturday afternoon that Cassidy's condition is "looking grim", according to one anonymous source with knowledge of the situation, and that Cassidy is experiencing organ failure.
His family have been told to prepare for the worst.
Although he is no longer in a coma, as first reported by TMZ, he remains in critical condition and in need of a liver transplant.
OSCE watchdog slams Unites States, Russia for 'foreign agent' media laws
Earlier on Thursday Russia named nine USA government-sponsored news outlets likely to be labelled "foreign agents". It was seen as a quick response to the latest development of Russian media's situation in the United States.
Earlier this year, David revealed his battle with dementia.
'I want to focus on what I am, who I am and how I've been without any distractions.
The actor is best known for his role as Kevin Partridge in the 1970s musical sitcom The Partridge Family, causing him to become a popular teen idol and pop singer. I want to enjoy life'.
After his own diagnosis, the performer made the decision to stop touring as a musician so that he could concentrate on his health.