Hi Help Thank you for getting in touch. There are two things: A positive result at any time post exposure is a reliable result. A negative result may not be reliable until approximately 12 weeks or 3 months post exposure. The reason for this is not specifically to do with the test but more to do with what the tests look for. All available HIV self tests look for antibodies that your body creates. Each person creates these antibodies at slightly different times after infection. Some people create the antibodies after 4 weeks some not until 12 weeks. No available HIV self test can detect before the individual has created these antibodies. The anti body creation process is part of what you might have heard termed "seroconversion!. This is why we say that you cannot rely on a negative test result before 12 weeks, the point by which all people will have completed seroconversion. This is the same for all HIV self tests, despite some other manufacturers claims to the contrary. At 8 weeks post exposure it is thought that 95% of people will have completed this process. So a negative result at 8 weeks is extremely encouraging, but cannot be taken as conclusive. I hope that this answers your question. Kind regards Gary Carpenter BioSure (UK) Limited