Truvada, a combination of two drugs (tenofovir and emtricitabine) in one pill, reduces your risk of contracting HIV from a positive partner by as much as over 99 percent if taken each day as pre-exposure prophylaxis, or PrEP. But there are common problems associated with popping this little blue pill.

According to Truvada’s website, some people report abdominal pain, headaches and weight loss, especially during the first few weeks of taking the drug. In some cases when the med is taken long-term, more serious issues, such as liver, kidney and bone problems, may arise.

For this reason, those on PrEP should have their health care providers regularly test for loss of bone mineral density and kidney and liver functions and undergo screenings for sexually transmitted infections and HIV. In addition, clinical guidelines recommend that women get a pregnancy test at each follow-up visit.

Furthermore, individuals who suffer side effects from PrEP should let their doctors know. And if a problem occurs that’s not noted on Truvada’s label, the drug’s makers advise that you inform the FDA.