Prince reportedly had been diagnosed with AIDS six months before he died.
The 57-year-old musician passed away at his Paisley Park estate in Minneapolis last week and it has been alleged that he contracted HIV in the Nineties before developing full-blown AIDS last year after refusing medication for the illness on religious grounds.
Friends of the late star - who was a Jehovah's Witness - told the National Enquirer magazine: "He was in bad shape. Doctors told Prince his blood count was unusually low and that his body temperature had dropped dangerously below the normal 98.6 degrees. He was totally iron deficient, very weak and often disoriented. He rarely ate and when he did it all came right back up."
However, Prince is said to have told his friends: "God can - and will - cure me."
After his initial HIV diagnosis, Prince was reportedly discouraged from taking medication by members of his faith.
A source said: "They told Prince he'd have everlasting life and believed he had been cured by faith.
"But the symptoms returned and it was too late for medication. He expected to live through the summer but his immune system was very weak."
He is alleged to have been taking prescription opiates for "AIDS-related pain and hip problems".
These claims come following recent reports that Prince overdosed on the painkiller Percocet six days before his death and had to be given a "save shot" to counteract the effects of opiates, after being taken ill on his private jet on the way back from a gig in Atlanta.
According to friends, Prince knew he was dying and had already started planning his funeral.
A post-mortem was carried out on Prince's body last week and it confirmed there had been no trauma or violence in the time leading up to the singer's death.
The star's body has now been released to his family.