According to the National Cancer Institute, a normal prostate-specific antigen result is generally considered to be below 4 nanograms per milliliter. Doctors often recommend a prostate biopsy for men with higher PSA levels to determine whether prostate cancer is present.
Recent research cited by the National Cancer Institute suggests that PSA levels may rise if the patient has prostatitis or a urinary tract infection, and a prostate biopsy or surgery can also elevate the PSA level. Certain drugs, including finasteride and dutasteride, can artificially lower PSA. In general, however, higher PSA levels correlate with a higher likelihood of prostate cancer. Also, a continuous rise in PSA over time may also be a sign of prostate cancer.