Clinical guidelines recommend periodic lab testing while on PrEP for several reasons. First, we want to confirm that you remain HIV-negative while on PrEP, as do virtually all persons who use PrEP as directed to prevent HIV infection. While kidney dysfunction on PrEP is exceedingly rare, we keep an eye on your kidney health, which requires a blood test. Also, we care about your overall sexual health, and that involves periodic STI screening – necessary because most STIs are present without any symptoms. Comprehensive STI screening requires one blood test as well as urine and swab samples. We’re here to keep you healthy!