Prostate-specific antigen (PSA) is a protein produced by cells of the prostate gland. The PSA test measures the level of PSA in the blood, and can be used to detect disease (like prostate cancer); it is sometimes called a biological marker or a tumor marker. The doctor takes a blood sample, and the amount of PSA is measured in a laboratory.
It is normal for men to have a low level of PSA in their blood; however, both prostate cancer or benign (not cancerous) conditions can increase a man’s PSA level. As men age, both benign prostate conditions and prostate cancer become more common.