The PSA blood test scans for the level of the prostate-specific antibody. High PSA levels are associated with the development of prostate cancer, but low PSA levels can also be an indicator of health concerns.
Men who have a PSA level below 4 ng/ml (which is typically considered normal, according to the National Cancer Institute), have been found to be at risk for developing prostate cancer within 20 to 25 years, according to the American Cancer Society.
Very small increases in men with a low PSA level are also considered to indicate an increased risk for prostate cancer, according to the Urological Institute of Johns Hopkins Medical Institutions.
More than 15 percent of men with a low PSA level may be diagnosed with prostate cancer, according to the National Cancer Institute.
The normal level of PSA varies based on age and race, and readings vary across laboratories, according to the National Cancer Institute; therefore, a doctor can best help an individual understand what his PSA level indicates.
A man who is undergoing hormone therapy as part of his treatment for prostate cancer may have an abnormally low level of PSA. According to the National Cancer Institute, it may be necessary to wait for a time after stopping treatment to get a true reading of his PSA level.