It is possible for a person with HIV to have a negative antibody test result. When HIV infection is in the window period, the body has not yet produced enough antibodies to be negative, even though there is a viral infection. It takes a certain amount of time for the body to produce enough antibodies from the time of HIV infection, and this period is called the window period. According to the current testing technology used in most hospitals, the window period for antibody testing is about 2-6 weeks, with individual differences. To summarize, the antibody test can be negative when the HIV patient is in the window period, so it is recommended that people with high-risk behaviors should be tested after the window period and retested at the end of 3 months to make a clear diagnosis.