Many doctors are missing the signs that patients could be infected with HIV, researchers said after they found that one in four people with the disease could have been diagnosed at an earlier stage.
The British HIV Association (BHIVA), the body that represents HIV care professionals, said that patients with HIV are being denied longer life expectancies because they are being diagnosed too late.
A quarter of patients missed an opportunity for their HIV infection to be detected earlier because they were not offered a HIV test, according to BHIVA's audit of HIV testing and diagnosis in the UK.
Researchers said late diagnosis of the condition is a growing problem.
People who are diagnosed with more advanced HIV have a tenfold increased risk of death in the first year compared to those diagnosed with earlier stages of infection, they said.
The author of the report, Dr Ed Ong said: "Our data shows one in four people living with HIV could have had their condition diagnosed earlier.
"This is a serious wake-up call, and shows we need a pro-active and widespread testing programme which is tailored to those people who are most at risk."
BHIVA chair Professor Jane Anderson added: "Late diagnosis is the single biggest cause of death from HIV in the UK. It increases the risk of HIV related ill-health, of HIV being acquired by others, and significantly increases the costs of treatment.
"HIV is treatable, and if diagnosed in time, people with HIV can expect to have long and healthy lives. Sadly, opportunities for longer life expectancy for people with HIV are being thrown away by late diagnosis."
The research, which examined the records of more than 1,000 patients at HIV treatment centres in the UK, was published today in the Clinical Medicine Journal.