Low levels of PSA, or prostate-specific antigen, are considered desirable, since they indicate a lower risk for prostate cancer; readings below 4 nanograms per milliliter are considered normal, according to Health Magazine. Higher readings may indicate that cancer of the prostate is present.
PSA levels in men in their 50s or younger should be below 2.5 nanograms per milliliter, according to MedlinePlus. PSA levels in older men are slightly higher. Interpretation of PSA tests depend on several factors, including a man’s ethnicity, age and any medications that he is taking.
Prostate-specific antigen is a type of protein that is manufactured by the prostate cells. To check for the level of PSA in the blood, a blood sample is collected. Doctors typically order this test as a screening for prostate cancer, to check the effectiveness of prostate cancer treatments, or to determine if there is a recurrence of cancer. Sometimes the test is ordered when a physical exam reveals a prostate gland that feels abnormal, states MedlinePlus.
One of the biggest benefits of PSA screening, according to MedlinePlus, is that it can catch prostate cancer in its earliest stages. Still, the test is not a diagnostic tool for prostate cancer. To make a definitive diagnosis, a prostate biopsy is required.