We’re very lucky in the UK. We have some of the best HIV treatment centers in the world. What’s more, they’re open to everyone regardless of people’s ability to pay. One of the great success stories is nearly everyone diagnosed with HIV is linked into follow-up care and gets access to treatment.

However there’s one area where we’re performing very badly. Shockingly, around one in four people infected with HIV are still unaware they have the virus. I believe changing this statistic is the most important thing we can do in the fight to finally beat HIV. I want to explain why I feel this is so important and what we can do about it.

First of all, reducing undiagnosed HIV is important because it keeps people well. Late diagnosis is the leading cause of HIV related illness and death. Those who know they have HIV early on can do something about it. By starting treatment at the recommended time they can expect to live long, healthy lives.

However, about 40% of HIV in gay men is diagnosed after the time treatment is recommended. This delay makes it less effective. Studies show people who find out late are 10 times more likely to die in the following year. It makes me angry gay men are still needlessly becoming ill and dying when we have the opportunity to prevent it.

Secondly, undiagnosed HIV fuels the spread of new infections. The Health Protection Agency recently released a jaw-dropping statistic. They estimate that 82% of HIV in gay men is caught from an undiagnosed partner. Yes, that’s four out of every five new cases.

The bottom line is that you are much more likely to catch HIV from having unprotected anal sex with someone who hasn’t had a recent test than an HIV positive person who is taking effective HIV treatment.

Reducing undiagnosed HIV is an important tool to stop HIV transmission. The vast majority of people who know they have the virus take steps to protect their sexual partners. Both condoms and starting HIV treatment massively reduce the risk of passing HIV to others.

It’s been shown that a shift of just 1% towards earlier HIV diagnosis would make a big difference with 3,500 fewer transmissions within five years. This isn’t just good for gay men’s health. It would also save the National Health Service £18million ($28million â‚¬21million) per year in England alone.

It’s recommended all gay men test every 12 months. You should test every three months if you are having unprotected sex with new partners. The sad fact is the majority of gay men in this country haven’t tested in the last year. That’s why I believe HIV testing should be made as easy as possible. Many clinics like my own, 56 Dean Street in London, offer walk in HIV testing services with one minute results.

What about men who find it difficult to get into a clinic? Some services are beginning to pilot home testing.

You order a test kit online and then return the sample in the post for laboratory testing. The Dean Street at Home service has already been running for 15 months and it’s available to all gay men living in London within the M25.

The kit uses a mouth swab sample. If the test reacts we’ll be there for you on the phone to provide support and to arrange follow-up tests in a specialist clinic. Negative results are sent by text.

Thousands of gay men have already used Dean Street at Home and 96% of users said they would recommend it to a friend. It’s making a real difference and identifies around 3% of all new HIV in London’s gay men. If you haven’t tested in the last 12 months why not order a test kit now here.

Dr Alan McOwan is director of services and lead clinician at 56 Dean Street, the sexual health clinic in London’s gay district of Soho.