If you are infected with HIV, it usually takes from three weeks to two months for your immune system to produce HIV antibodies. During this "window period" you can test "negative" for HIV even if you are infected. If you think you were exposed to HIV, you should wait for two months before being tested. You can also test right away and then again after two or three months. If you are infected, you can transmit HIV to others during the window period even if you test negative. In fact, during this period of early infection, you have the greatest chance of passing HIV infection to others. About 5% of people take longer than two months to produce antibodies. Testing at 3 and 6 months after possible exposure will detect almost all HIV infections. However, there are no guarantees as to when an individual will produce enough antibodies to be detected by an HIV test. If you have any unexplained symptoms, talk with your health care provider and consider re-testing for HIV.