Abdelbaset Ali Mohmed al-Megrahi was taken to the intensive care unit of a private hospital in Tripoli on Friday, and received a transfusion of 11 litres of blood after his health began to deteriorate.
However, his brother, Abdel Hakim al-Megrahi, said his brother had subsequently felt strong enough to return home.
“His health is going from bad to worse, but he felt ready to go and his family took him home,” Abdel Hakim said.
Megrahi was convicted in 2001 of the 1988 bombing of Pan Am Flight 103 as it flew to New York from London. All 259 people aboard the airliner died and 11 others on the ground in Lockerbie were killed by falling wreckage.
Megrahi was diagnosed with terminal prostate cancer in October 2008 and released from Greenock Prison, Inverclyde, in August 2009 on humanitarian grounds less than a year later.
Doctors estimated that he had just three months to live.
His release angered many relatives of the victims, 189 of whom were American, and the Obama administration criticised the decision.
A number of American politicians have pressed for his extradition to the United States, something Libya’s ruling National Transitional Council said it would not do.
Megrahi, who served as an intelligence agent during the rule of Libyan dictator Muammar al-Gaddafi, denied any role in suspected human rights abuses in his home country before Gaddafi’s fall and death in a popular uprising last year.
Since returning to Libya, Megrahi has made very few public appearances.
He has always maintained he is innocent of the crime and his family has said on a number of occasions that he is near death.