The home secretary and a host of cross-party MPs have been tested for HIV - to encourage others to do the same.
Amber Rudd took the blood test with Green Party co-leader Caroline Lucas, Public Health Minister Steve Brine and Labour's Liz Kendall to promote National HIV Testing Week.
The Terrence Higgins Trust said early diagnosis could help people with HIV live long, happy and healthy lives.But figures suggest about 10,700 people do not know they have HIV.
Ms Rudd and a number of MPs had been tested in their parliamentary offices, while others had attended the Terrence Higgins Trust HQ in King's Cross, London, or visited local services in their constituencies.
Afterwards, the home secretary tweeted: "Despite the look on my face, the pain wasn't that bad! Just took an HIV test with Terrence Higgins Trust to raise awareness for HIV Testing Week."
Liam Beattie, the charity's campaigns and parliamentary officer, said: "While we've seen some major steps in HIV in recent years, the number of late diagnoses and undiagnosed people living with HIV is still a cause for concern.
"It's vital that we enable people to feel empowered to test and know their status and dispel the myths that surround testing for and living with HIV, which no doubt support from a number of prominent MPs will hugely help."