The “normal” PSA serum concentration ranges between 1.0 and 4.0 ng/mL. However, since the prostate gland generally increases in size and produces more PSA with increasing age, it is normal to have lower levels in young men and higher levels in older men. The PSA level also depends on ethnicity and family history of prostate cancer. Other than the single reading, the changes in PSA numbers on an annual basis (also referred to as PSA-velocity) also play a role in decision making about the PSA marker.