PrEP can cause nausea, diarrhea, headaches, and weight loss. These symptoms affect a small number of people. About 9% of people on Truvada experienced nausea, the most commonly reported symptom, while 2% experienced weight loss. The symptoms typically subside after the first month of use. In addition, PrEP can lead to slightly reduced kidney function. In rare cases, it can liver damage and loss of bone density, which can put someone at a risk of bone fractures. Doctors monitor kidney function, liver function, and bone density in people on PrEP to ensure it isn’t causing harm. If you have kidney or liver issues or osteoporosis, let your doctor know before you start PrEP.