HIV can be detected by blood tests at different times after exposure, depending on the type of test used. The earliest detection is possible with nucleic acid tests (NAT), which can usually detect HIV 10 to 33 days after exposure. Fourth-generation antigen/antibody tests, which detect both HIV antibodies and the p24 antigen, can typically detect HIV infection 18 to 45 days after exposure when done with blood from a vein. Tests using blood from a finger prick or oral fluid have longer detection windows, up to 90 days. Rapid antibody tests typically detect HIV within 23 to 90 days after exposure. For the most accurate results, testing should be done after these window periods and may require follow-up tests to confirm. Key details:

• NAT: detects HIV 10 to 33 days post-exposure.
• Fourth-generation lab antigen/antibody test (venous blood): detects HIV 18 to 45 days post-exposure.
• Fourth-generation finger prick test: up to 90 days detection window.
• Rapid antibody tests: 23 to 90 days detection window.
• Negative results before the window period ends may require retesting for confirmation.