Before you start using PrEP, it is essential to make sure you are HIV negative; you run a small risk of developing HIV drug resistance if you are already infected with HIV when you start PrEP. That’s because Truvada is not sufficient on its own for treating HIV; if you are already infected, the virus in your body could become resistant to the two drugs in the Truvada pill. HIV drug resistance means certain medications will no longer keep the virus in check if you are HIV-positive. For this reason, it is really important that before you start using PrEP, you get tested for HIV using an RNA test, which looks for the actual presence of virus in your blood. During early HIV infection, it’s a more reliable test than the standard antibody test, which looks for the presence of antibodies to HIV, not the virus itself.
When you are using PrEP, you are advised to get tested for HIV every three months to make sure this HIV prevention strategy is working for you.