TMZ said Cassidy is suffering from organ failure and unless he gets a liver transplant soon he could soon die.
"He is in the hospital and it's not looking good", a source told E!
It is unclear what is causing his organs to shut down.
Smokers Find Help Through Group Support Counseling
Don't smoke? You can still participate in The Great American Smokeout by encouraging your loved ones to kick the habit. According to the Centers for Disease Control, almost 160,000 people die each year from lung cancer caused by smoking.
Later that month, he appeared on "Dr. Phil" to describe his battle.
Partridge Family alum David Cassidy was recently hospitalized and his family has rushed to his side. I want to love.
Cassidy, aged 67, is "now conscious" and "surrounded by family", a representative said. Cassidy, whose grandfather and mother also were stricken with the memory-loss disease, told the magazine of his diagnosis, "I was in denial, but a part of me always knew this was coming".
Millions more of Americans may now have high blood pressure
The changes were announced at the American Heart Association's 2017 Scientific Sessions conference in Anaheim, California. High blood pressure is the No. 2 cause of preventable heart disease and stroke behind smoking, Gandhi said.
The actor and singer was in pain and taken to hospital on Wednesday (local time), the representative added.
Cassidy, who comes from a show business family, skyrocketed to fame for his role at Keith Partridge on the 1970s sitcom The Partridge Family, which aired from 1970-1974.
Saudi-led coalition air raid puts Yemen's Sana'a airport out of service
Some UNHCR staff have also been affected, with some stranded outside the country and others lacking fuel for transport. However, Mr McGoldrick said there was "no indication" yet of the blockade being lifted.