What is PSA (Prostate Specific Antigen)?

It is a protein produced by the prostate

It is used as a “disease marker” to represent prostate cancer.

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Disclaimer: This information isn’t a substitute for professional medical advice, diagnosis, or treatment. You should never rely upon this article for specific medical advice. If you have any questions or concerns, please talk to your doctor.

PSA, or Prostate Specific Antigen, is a protein produced by the prostate and found mostly in the semen, with very small amounts released into the bloodstream. It is used as a “disease marker” to represent prostate cancer. When there’s a problem with the prostate—such as the development and growth of prostate cancer—more PSA is released. PSA eventually reaches a level where it can be easily detected in the blood. This is often the first indicator of prostate cancer.

During a PSA test, a small amount of blood is drawn from the arm, and the level of PSA is measured. Doctors look at the overall level of PSA, as well as its rate of rising (velocity) compared with prior test results. As the PSA number goes up, the chance that cancer is present increases. Men whose levels go above 3 or 4 are often recommended to undergo a biopsy; however, this PSA level does not mean that prostate cancer is definitely there, and some cancers may be present even when PSA levels are lower, particularly among younger men.


PSA is not a perfect test to screen for prostate cancer. Elevated levels can be caused by other benign prostate diseases and problems, such as BPH (benign prostatic hyperplasia, an enlarged prostate) or prostatitis (an infection in your prostate). There is an active debate around prostate cancer screening. Some health care professionals are concerned that increased PSA screening is finding tumors that are so slow-growing as to pose no long-term threat to the patient. Some think this can lead to “overtreatment” in many men with low-risk cancers, causing unnecessary side effects and quality-of-life impact. However there is a lot of data to suggest that PSA testing has reduced the death rate from prostate cancer, because men with aggressive cancers are diagnosed earlier— often before the cancer has spread—and can be cured and/or more effectively managed by earlier treatment. If PSA screening is done well, its value is greatly increased. It is critical to test men at the appropriate age, repeat PSA tests once the baseline level is known, and reserve treatment for those with higher risk cancers. The Prostate Cancer Foundation is actively funding new research into better prostate cancer screening tests that are more specific and sensitive than the PSA test.

PSA screening decisions should be made in consultation with your doctor and based on a full examination of risk factors.

In men who have confirmed diagnosis of prostate cancer, rising PSA is a useful test to track prostate cancer growth, since it can be detected well before any clinical signs or symptoms. The PSA is also widely accepted as an invaluable tool for monitoring prostate cancer disease activity and recurrence of prostate cancer after treatment.

To learn more, please visit the Prostate Cancer Foundation at PCF.org.

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