The 31-year-old was injured in a fall earlier this week and was admitted to hospital Wednesday. The former Olympian remains in the care of specialists as he faces his well-publicised battle against depression and alcohol abuse, reported Xinhua.
In his autobiography published in 2012, Thorpe said he had struggled with the same.
"Not even my family is aware that I've spent a lot of my life battling what I can only describe as crippling depression," wrote Thorpe, who has won five Olympic golds, most by an Australian but failed in his bid to make a comeback at the 2012 London Olympics.
A close friend of Thorpe said Thursday that he had an accident at home.
"He slipped and hurt himself. We're hoping he's going to be okay and make a full recovery," the friend said.
Broadcaster Alan Jones, one of Thorpe's closest friends, said the swimmer had been going through some problems recently.
"It's serious but there's not a lot I can or want to add. Ian is a beautiful person but he has difficulty recognising his problems," Jones said.