Andrew Stimpson was diagnosed as HIV-positive in August 2002 but tests 14
months later showed the virus had vanished from his body, according to hospital officials.
The 25-year-old man from Largs in Scotland, told two British newspapers he felt special and blessed to have been "cured" and pledged to help medics in their fight against the condition, which usually leads to AIDS.
Mr Stimpson declared he was "one of the luckiest people alive".
Chelsea and Westminster Healthcare NHS Trust confirmed the tests were accurate and no mix up had occurred but doctors say they cannot confirm his cure because he has refused further tests.
“This is a rare and complex case. When we became aware of Mr Stimpson's HIV negative test results we offered him further tests to help us investigate and find an explanation for the different results,” the Trust said in a statement.
"So far Mr Stimpson has declined this offer."
A trust spokeswoman added: "We urge him, for the sake of himself and the HIV community, to come in and get tested.
'Unbelievable'
Mr Stimpson said there are 34.9 million people with HIV globally and that he was just one person who had managed to control it, and ultimately purge it form his body.
"For me that is unbelievable - it is a miracle."
Experts say there is anecdotal evidence from Africa of people being cured of HIV but they warn that the virus can also retreat to undetectable levels.
Some HIV sufferers are considered “slow progressors” and can fight off developing AIDS for up to 20 years.
Mr Stimpson has unsuccessfully claimed for compensation, saying he became depressed and suicidal after being told he was HIV-positive but remained well and did not require medication.