A Prostate-Specific Antigen (PSA) test is a blood test that measures the level of PSA in a sample of your blood. PSA is a protein made by your prostate. The prostate is a gland in the male reproductive system. It lies just below the bladder. It makes the fluid part of semen.
It's normal to have a low level of PSA in your blood. A high PSA level may be caused by an enlarged prostate, prostate cancer, a prostate infection and certain medications.