###Human: What is the frequency to do HIV testing while taking PEP? ###Assistant: Hi. The answers to your queries are: For PEP (post-exposure prophylaxis) efficacy, adherence to the medications prescribed for PEP is the most important thing. PEP is really efficacious, To the best of my clinical practice, I have not seen any case of a patient who has completed PEP with complete adherence and then turned positive. There are recommendations to test at four weeks, three months and then at six months of last exposure. You need not be tested in between and if negative, no further test is required.