Hi Brad101, The BioSURE self-test has a 12 week window period so I would recommend to retest at 12 weeks for a conclusive result. The accuracy of the test does not change throughout the window period and is 99.7%. But of course, if a person has tested within the window period, the result cannot be wholly relied upon as that individual may not have produced a detectable level of antibodies for the test to accurately give a result. And although a negative result at 11 weeks is a very good indication of a negative HIV status, I would recommend to retest again at 12 weeks just to be sure. I hope this information helps. Kindest regards, Becky, BioSURE UK LTD