In 2010, half (3,300 of 6,600) of adults aged 15 and over, and newly diagnosed were diagnosed at a late stage of HIV infection.

People diagnosed late have a ten-fold increased risk of death within 1 year of HIV diagnosis compared to those diagnosed promptly (4.0% vs. 0.4%). Overall, 90% of people who died within a year of HIV diagnosis between 2000 and 2009 were diagnosed late. Late diagnosis also means that a person has remained unaware of their HIV status for many years, increasing the risk of onward transmission.  

A late diagnosis means having a CD4 count below 350 cells/mm³ within three months of diagnosis. Previously it meant having a CD4 count below 200 cells/mm³ within 91 days of diagnosis; this is now referred to as a very late HIV diagnosis.

How does this vary by probable exposure category?

In 2010, the proportion of late diagnoses was lowest among men who have sex with men and highest among heterosexual men. 

Probable exposure category	% of newly diagnosed adults aged 15 and over in 2010 that had a CD4 count below 350 cells/mm³ within 91 days of diagnosis	% of newly diagnosed adults aged 15 and over in 2010 that had a CD4 count below 200 cells/mm³ within 91 days of diagnosis
Men who have sex with men	39%	18%
Heterosexual women	58%	34%
Heterosexual men	63%	40%
Overall	50%	28%

*Please note that all percentages are rounded and may not add up to 100%

This information is based on estimations made by the Health Protection Agency, sourced from their HIV in the United Kingdom 2010: 2011 Report.