Health Encyclopedia


Tests & Procedures

Prostate-Specific AntigenAntígeno prostático específico

Prostate-Specific Antigen

Does this test have other names?


What is this test?

This test measures the level of prostate-specific antigen (PSA) in your blood.

The cells of the prostate gland make the protein called PSA. Men normally have low levels of PSA. If your PSA levels start to rise, it could mean you have prostate cancer, benign prostate conditions, inflammation, or an infection.

PSA testing is controversial because the U.S. Preventative Services Task Force discourages men who don't have any symptoms of prostate cancer from being screened. The task force says that PSA test results can lead to treating small cancers that would never become life-threatening.

But the American Cancer Society believes men should be told the risks and benefits of PSA testing and allowed to make their own decision about if and when to be screened.

Why do I need this test?

You may have this test if you are 50 or older and your doctor wants to screen you for prostate cancer. Some doctors recommend screening at age 40 or 45 if you have a family history of prostate cancer or other risk factors.

You may also have this test if you have already been diagnosed with prostate cancer, so that your doctor can monitor your treatment and see whether your cancer has come back.

What other tests might I have along with this test?

Your doctor may also do a digital rectal exam (DRE). A DRE is a physical examination of the prostate, not a lab test. For the exam, your doctor will place a gloved finger in your rectum and feel the prostate to check for any bumps or abnormal areas. The FDA recommends that a DRE be done along with a PSA test.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Results are given in nanograms per milliliter ng/mL. Normal results are below 4.0 ng/mL. A rising PSA may mean that you have cancer. But the PSA results alone won't tell your doctor whether it's cancer or a benign prostate condition. If your doctor suspects cancer, he or she will likely suggest that you have a biopsy of the prostate to make the diagnosis.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

An infection can affect your results, as can certain medications. Riding a bicycle and ejaculation may also affect your results.

How do I get ready for this test?

You may need to abstain from sex and not ride a bicycle within one or two days of the test. In addition, be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.


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