Guatemala City, with one lawyer saying he had suffered two mild heart attacks and another describing "heart problems" and chest pains.
The 67-year-old was later discharged and taken back to his cell, with a hospital official saying he showed signs of anxiety and high blood pressure -- but no life-threatening condition.
It was the latest dramatic twist to the incredible saga surrounding the Silicon Valley legend whose thrill-seeker life reportedly descended into out-of-control hedonism centered on experimental drugs and prostitutes.
McAfee's neighbor on the palm-fringed Belize island of Ambergris Caye, 52-year-old Florida expat Gregory Faull, was discovered on November 11 by his housekeeper with a 9-mm slug in his head, lying in a pool of his own blood.
Prior to his murder, Faull had orchestrated a letter of complaint to the local mayor, urging the authorities to take action because McAfee's "vicious" dogs and aggressive security guards were scaring tourists and residents.
McAfee shot dead four of his dogs before fleeing, claiming they had been poisoned by Faull. Police in Belize said weeks ago that ballistics experts were seeking a match between bullets founds in the dog carcasses and one found in the murder victim, but no results have been announced.
McAfee has not been directly accused of Faull's murder, but official insistence that he is wanted only for questioning as a "person of interest" in the case could simply be a ruse to get him to give himself up.
The tattooed 67-year-old with a weathered face and manic eyes displayed a genius for self-publicity during more than three weeks on the run with his young girlfriend, Samantha Vanegas.
His whoismcafee.com blog contains a rich assortment of claims of innocence, rambling vents against what he called the corrupt Belizean government and misleading information intended to throw police off his scent.
At the weekend, he and his 20-year-old companion, accompanied by two journalists from the gonzo-style magazine Vice, stole across the border into Guatemala.
McAfee secured the services of top defense attorney Telesforo Guerra, a former Guatemalan attorney general, and announced on Tuesday that he would be seeking political asylum because he feared for his life in Belize.
McAfee made his formal request for asylum after being arrested on Wednesday, claiming through his attorney that he was a "victim of persecution and harassment" by the Belizean government.
Guatemalan President Otto Perez rejected that petition on Thursday and foreign minister Harold Caballeros said McAfee would be sent back to Belize.
Hours later, McAfee was found prostrate on the floor of his cell after complaining of chest pains, according to media reports. Taken away by ambulance, nurses strapped him to a gurney before wheeling him into hospital.
Guerra, who has filed a habeas corpus petition to delay McAfee's deportation, told journalists before his client was discharged from hospital: "He says he feels fine. They prescribed medication and he is taking it."
As the dramatic events were unfolding, a last-ditch appeal was posted on McAfee's blog urging his supporters to email the Guatemalan president and ask him politely to reconsider.
In earlier posts, the increasingly desperate fugitive said the US embassy in Guatemala City had not been able to help and asked if anyone knew anyone at the State Department who could intervene.
In Washington, State Department spokesman Mark Toner told reporters he was aware of the McAfee case but couldn't give any more information due to privacy laws.
"While he can make statements, we can't really give you much detail in response," Toner said.
McAfee amassed an estimated $100 million fortune during the early days of the Internet in the 1990s, designing the pioneering anti-virus software that bears his name, before cashing out to become an intrepid adventure-seeker.
He decamped to Belize in 2009 after losing most of his fortune due to bad investments and the financial crisis.
McAfee was briefly incarcerated in April after police found him living with a 17-year-old girl and discovered an arsenal of seven pump-action shotguns, one single-action shotgun, and two 9-mm pistols.