According to the United States Department of Veteran Affairs, a negative HIV test means that no signs of HIV infection were detected. However, the implications of a negative HIV test depend on the sensitivity of the test performed, as well as the time elapsed between testing and possible exposure to HIV. In cases where test results may be in doubt, additional testing may be required to confirm the negative HIV result.
The U.S. Department of Veteran Affairs advises that antigen tests look for the presence of HIV virus. HIV antibody tests look for the presence of HIV antibodies. After infection with HIV, it takes about two weeks for the virus to replicate and produce enough antigen to be detectable, and it takes more than three weeks for the body to produce sufficient antibodies to be detectable through testing. So if not enough time has passed since the potential exposure, it is possible to obtain false negative results, necessitating further testing.