It is "unacceptable" that four in 10 people only find out they have HIV when it has started damaging their immune system, a leading charity has said.
Ahead of HIV testing week (November 19-25) Ian Green, chief executive of the Terrence Higgins Trust, called for a "culture shift" in attitudes to "demystify" the virus.
He added: "Testing is free, fast, confidential and has never been easier."
Embarrassing Bodies presenter Dr Christian Jessen said being checked can "sound like a daunting prospect, but honestly it isn't. Testing puts you in control."
He added: "Many people living with HIV do not know they have it - and are therefore likely to unwittingly pass on the virus.
"On the other hand, those who get a positive result and onto effective treatment can live a long and healthy life, and cannot pass on HIV to others. It's a no-brainer."
Green praised the "Prince Harry Effect" as demand for self-check kits increased fivefold "almost immediately" after the royal was pictured getting tested in July.
The prince, who has stepped up his work helping the fight against HIV, has talked of wanting to "smash the stigma" surrounding the illness.
Around 6,000 people were diagnosed in the UK last year with some 90,000 living with the virus and accessing care, according to Public Health England.
They said reducing late diagnosis was a "clinical priority" as those affected "have been living with an undiagnosed HIV infection for at least three years and are at risk of premature death and of transmitting the virus to their sexual partners".
Information for getting a HIV testing kit can be found here.