How the test is done

The test can be done in several ways. The most common method is to take a small sample of blood from a vein in your arm. The blood is sent away to a laboratory.

At most clinics you will need to make a second appointment to go back to the clinic to receive the result in person.

Some clinics and community organisations offer a test which gives you a result in one hour. This is usually done using a finger-prick blood test.

What a positive result means

A positive result means that you are infected with HIV. However, because the course of HIV infection is so variable this doesn't tell you anything about whether HIV has done any damage to your immune system, or whether you need to start taking treatment.

HIV is can be passed on in blood and in sexual fluids. This means that you should have safer sex with any sexual partners. If you use needles or syringes to inject drugs, you shouldn't share them. Taking these precautions will prevent anyone getting HIV infection from you – and protect you from other infections.

There is lots of information and support available to you if you have just found out you have HIV. Further information about living with HIV can be found on NAM’s website for people with HIV in the UK: www.namlife.org.

If you test positive for HIV, your doctor will also do more tests to find out how much damage HIV has done to your immune system. Your doctor will almost certainly want to discuss with you the treatments currently available to treat HIV, but you may not have to start taking treatment straight away.

What a negative result means

Finding out that you do not actually have HIV can be a weight off your mind.

But a negative result offers you no guarantees for the future. You need to continue to protect yourself by having safer sex and avoiding sharing needles and drug injecting equipment.

What’s ‘the window period’?

You may have heard, or read, about ‘the window period’ in HIV testing. This refers to the period of time after infection, before which tests are not able to reliably detect infection.

For example, most HIV tests look for antibodies, which are one of the body’s responses to infection. The body can generate antibodies against a wide variety of things including parasites, bacteria, viruses, allergens and poisons.

HIV antibodies don't appear the day after you become infected, so it is not possible to find out if you have been infected immediately after a possible risk. Antibodies usually take between two weeks to two months to appear in your blood. The time between infection and the development of antibodies is called the window period.

During the window period, people infected with HIV may have no antibodies in their blood, but they are likely to have very high levels of HIV in their blood, sexual fluids or breastmilk. In fact, a person with HIV can be extremely infectious during this window period, before their immune system has tried to control the virus. So they could pass on HIV to another person, even though an antibody test would say they were HIV-negative.

Different types of HIV tests have different lengths of window periods. Many clinics now use a test which looks for both antibodies and p24 antigen, and the window period for this is a few days shorter than that for an antibody-only test.

It used to be the case that someone with concerns about a possible HIV exposure would be advised to wait three months after a possible risk of exposure to HIV before being tested, to be sure that a negative result is truly negative.

However, if you have good reason to believe you may have been recently exposed to HIV, you should not delay in seeking advice. Most clinics would prefer you to take a test straight away, and to repeat the test a few weeks later.

Talking it over

You might find it useful to talk in confidence to someone at your local clinic or in an HIV voluntary organisation. In the UK you could also contact the following helplines anonymously:

Terrence Higgins Trust

THT Direct  0845 12 21 200: weekdays 10am-10pm, weekends noon-6pm

Black Health Agency

African AIDS Helpline  0800 0967 5000: Monday to Friday 10am-6pm