Normal levels of total PSA, or prostate-specific antigen, increase from less than 2.0 nanograms per milliliter under age 40 to less than 7.2 nanograms per milliliter above age 80, says Mayo Clinic. If the PSA level is higher than 10 nanograms per milliliter, the risk of prostate cancer is high.
High PSA results are used in conjunction with other tests to determine if a malignancy exists, notes Mayo Clinic, especially for PSA levels between 4.0 and 10.0 nanograms per milliliter. Doctors use the free:total PSA ratio to determine the probability of a male developing prostate cancer. A high ratio suggests the need for a prostate needle biopsy.