No specific level of PSA is considered normal, as men with heightened or low levels of PSA can still have prostate cancer, according to the National Cancer Institute. Doctors have historically considered PSA levels at or below 4.0 nanograms per milliliter to be normal, but this is no longer true.
Men with heightened levels of PSA should still pursue further testing, states the National Cancer Institute. This is because a long-term increase of PSA is more statistically significant than a single high reading. The validity of PSA test results can be questionable due to outside factors that may influence results, such as urinary tract infections or prostatitis. Additionally, some drugs are known to lower PSA levels.