A normal PSA level in an adult male according to the National Cancer Institute is 4.0 nanograms per milliliter or lower. However, studies show some men who have a lower PSA level do have prostate cancer while some men with higher levels do not have prostate cancer.
The prostate-specific antigen test measures a specific protein produced in the prostate gland. Men over 50 years of age are advised to have a PSA test done yearly and men with a family history of prostate cancer should have tests performed earlier at 40 to 45 years of age, recommends the National Cancer Institute. In a PSA test, a man's blood sample is analyzed, searching for an abnormal level of the antigen. The results of PSA levels are measured in nanograms per milliliter. Various non-cancerous factors can result in a man having a higher PSA level than normal.