The site reports that he had been out on an afternoon boozing session with a pal after meeting probation officials following his release from a jail term.
Fielder-Civil was reportedly found on Aug. 3 by current partner Sarah Aspin, choking on his vomit.
Citing a source, The Sun reports he had taken a packet of heroin and morphine he had obtained earlier in the day.
Fielder-Civil was rushed to a hospital in West Yorkshire, England where he has reportedly suffered multiple organ failures.
Amy Winehouse's father Mitch tweeted support today for Fielder-Civil, writing, "Terrible news about Blake this morning. Remember Amy loved him. Let's pray for his recovery."
Winehouse and Fielder-Civil were married from 2007-09, before the pair split. Winehouse died in 2011.