The initial screening test for Hep C is a simple blood test, known as the HCV (Hep C virus) antibody test. To fight the virus our body produces antibodies. This test does not look directly for the virus itself but for the antibodies, which indicate that you have been exposed to the virus and have produced antibodies to fight it. However, this test cannot determine whether or not you are still infected with the virus or for how long you have been infected.

Antibody test results are usually clearly positive or negative, but sometimes they come back as 'indeterminate', which may indicate that the person is in the process of seroconverting (see below) or becoming infected. In this case a repeat test will be required.

Approximately 25% of people who are exposed to Hep C will clear the virus spontaneously. It is not known why some people clear the virus, and they will still test antibody positive. There are different strains of Hep C virus however, and it is possible for a person to become co-infected with more than one strain. It is not safe to assume that you are safe from re-infection just because you already have Hep C.

Those who test positive for Hep C antibodies should then be given a PCR (polymerase chain reaction) test to look for the presence of the actual Hep C virus and to establish current infection. Like the Hep C antibody test, the PCR cannot tell how long someone has been infected. PCR is a laboratory technique that amplifies the virus's genetic material to a level that can be detected. This technique consists of many stages and can be expensive, although it is covered by Medicare if you meet certain criteria.

The results of these tests can be confusing, so it is wise to have them explained by someone who has a good grasp of Hep C and the meaning of test results. This should be covered in pre-test counselling, but unfortunately many people do not receive adequate counselling and information prior to testing.

It can take up to six months from the time of exposure or infection for antibodies to be detected in the blood. This is sometimes referred to as seroconversion, or the 'window period'. It is important for users who keep injecting unsafely or sharing injecting equipment to be retested six months after their last suspected risk.

Liver function tests (LFTs) are blood tests which help to indicate the degree of the damage the virus is doing to your liver at the time of the test, and are a different test to the antibody test (above). Unfortunately, LFTs cannot tell how much residual or structural damage the liver may have accumulated over the course of the infection. A doctor can offer ongoing evaluation of your liver health by interpreting differences in LFT results over time and whether or not you have physical symptoms or signs of liver disease. LFTs can be done monthly, quarterly, twice yearly or annually, depending on each individual case.

A liver biopsy is the removal of a small sample of liver tissue for examination under a microscope. A biopsy is usually performed at a hospital under a local anaesthetic and is the only test which can provide an accurate indication of the state of your liver and the degree of damage it has.

It is difficult to predict who will develop Hep C related liver disease and/or cirrhosis (see below), as it can take years to develop; again, a biopsy is necessary to determine whether treatment is required and/or likely to be effective.