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What a negative result means
A negative test result means that antibodies against HIV have not been found in your blood.
This probably means you don't have HIV infection.
But it can take up to three months to produce antibodies after infection with HIV. This is often called a window period. During this time the test could be negative even if you did have HIV infection and were infectious. In fact, you are most infectious during this window period before antibodies have been produced. So you might need to repeat a negative test to be sure of the result.
If there is a strong possibility that you have been exposed to HIV recently – within the last month or so – you should discuss with a doctor at a GUM clinic the possibility of early treatment, or testing with the p24 antigen test if this was not included in the initial screening test used. See If you may have been exposed to HIV recently below.
A small number of people - probably one in a hundred of those who become infected - take more than two to three months to form antibodies, but it is highly unusual to take more than six months to form antibodies.
A very tiny percentage of people with HIV infection - one in a hundred thousand - never seem to develop any antibodies at all.
Obviously a negative result offers you no guarantees for the future. So whatever the result of the test you need both to have safer sex (see Safer sex) and to avoid sharing needles and injecting equipment when injecting drugs (see Drug use).