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, where it is subjected to a procedure that quickly allows trained laboratory staff to recognise whether it contains antibodies. If the blood gives a negative reaction on the first test, it can be safely assumed that no HIV antibodies are present in the blood, and you are not infected. If the blood appears to give a positive reaction to the testing procedure, however weak, a confirmatory test of a different sort is done to check the presence of HIV antibodies.

At most clinics you will need to make a second appointment to go back to the clinic to receive the result in person. HIV antibody test results should not be given out over the phone or sent through the post by STI clinics.

HIV antibody testing can also be done by taking a sample of saliva from the margin of the gums, but this method is only used for HIV testing with injecting drug users at present.

Waiting for a result how long must I wait?

Test results may take up to two to three weeks in some cases, because STI clinics send their blood samples off to laboratories in batches. Some districts or regions are quicker than others.

Some clinics may be able to supply test results more quickly if you are very distressed.

Same-day or overnight testing services now exist across the country on certain days of the week. These provide pre– and post–test counselling. Testing through these clinics can reduce the anxiety of waiting for a test result, but appointments may need to be booked several weeks in advance, so they may not provide instant answers.

If a test result is needed in a hurry – for instance for employment reasons – the other option is to go to a private clinic. These may charge anywhere between £20 and £70 for a test, and may not provide pre–test or post–test counselling. Private clinics are almost exclusively confined to London.

If you did get a positive result, you would do much better to be an outpatient of an NHS HIV clinic. These have much more experience in treating HIV infection.

Does the test show when infection occurred?

Normal HIV antibody testing does not give any information about when infection occurred, unless of course there are previous negative results. However, additional information - including the results of CD4 tests, clinical assessment, and other people's HIV status - may give clues.

Detuned antibody tests (discussed in The scientific basis of HIV antibody testing) may suggest recent infection, but these currently seem more appropriate for comparing populations, rather than telling when individuals were infected.

See NAM's The HIV & AIDS Treatments Directory or aidsmap.com for further discussion of these issues.

Home testing

The sale of HIV testing kits of any sort for private use is illegal in the UK, and will remain so for the foreseeable future. HIV testing should only be conducted by qualified medical professionals, and HIV testing should be accompanied by counselling.

Rapid tests

Rapid HIV tests are widely used in resource-limited settings. The need for immediate HIV test results to make treatment decisions and to assist with prevention strategies portends their increased use in developed countries as well.  Rapid HIV tests demonstrate sensitivities and specificities comparable to those of enzyme-linked immunoassays (ELISAs) currently used for screening. Algorithms comprised of a combination of two or more rapid tests produce HIV test results with predictive values comparable to those of the ELISA-Western blot combination. Rapid HIV tests offer additional advantages of low cost and same-day results and are likely to gain increasing acceptance for HIV screening and diagnosis in both developed and developing countries.