An HIV test will only detect the virus four weeks after infection. Before this four-week period, the virus is not detected by a test. However, if you think you have been exposed to the risk of HIV, you should not wait for the four-week window period to pass before seeking help.
People who have recently been infected with HIV often experience a short, flu-like illness two to six weeks after infection. Symptoms include fever, sore throat, and body rash. You can only be certain you have HIV if you have an HIV test. The sooner you are tested for HIV, the sooner you find out whether you need treatment.
Read more about HIV testing from HIV Aware.