There is no harm in taking an HIV test straight after a potential exposure. However, you need to be aware that a false-negative result may occur if a sample is collected in the window period post exposure. This window period refers to the time between exposure and when a laboratory test can detect the infectious agent.
DNA Testing Center of America uses a 4th generation test for HIV that can detect an HIV infection within 18 - 45 days, or sometimes as early as two weeks post-exposure. Individuals who have been potentially exposed to HIV should be tested immediately, and then tested again at six weeks, three months, and six months.
If a recent exposure is suspected, an HIV nucleic acid test may be requested as these tests can usually detect HIV within 10-12 days of exposure.
In addition, if an individual is concerned about being exposed to HIV in the last 72 hours, they should be referred to a health care provider immediately for post-exposure prophylaxis (PEP) evaluation.