What Does a PSA Test Tell You?

Screening and Diagnostic Tool for Prostate Cancer

Anthony Camarda, 84, smiles as he gets his free PSA blood test. Credit: New York Daily News Archive / Contributor / Getty Images

Question: What Is a PSA Test?

My doctor has ordered a PSA test for me and I am not sure exactly what the test is and what my results should be. I am 59 years old and have been having trouble with urination lately. At night, I feel the urge to urinate, but cannot go. I have been told that this is a symptom of prostate cancer and should have a PSA test done.

The Purpose of the Prostate-Specific Antigen Test 

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

Prostate-specific antigen is a protein produced by the prostate gland. Men with prostate cancer often have elevated PSA levels, but levels can fluctuate for a variety of reasons other than prostate cancer.

For men who are experiencing symptoms related to prostate cancer, such as difficulty urinating, the PSA test can be an effective screening method. However, the test is notorious for producing false positives and negatives and is not considered an effective stand-alone diagnostic tool. It is used in conjunction with digital rectal exams and ultimately, a prostate biopsy, to confirm or rule out cancer.

How the Prostate-Specific Antigen Test Is Done

The test consists of a simple blood draw, and results are generally available within hours to a few days, depending on the lab facility your physician uses.

A low level of PSA in the blood is ideal. Higher levels of PSA in the blood increases the likelihood of prostate cancer, but you have to remember that false positives are common with the test.

PSA is measured by nanograms per millimeter (ng/mL) of blood. Most healthy men have under 4 ng/mL.

What Can Cause an Elevated PSA?

There are many things that can cause an elevated PSA level. Certain medications can cause it to rise, so it's important to make your doctor aware of all medications that you take, including prescribed medication, over-the-counter medication, and any herbs or homeopathic supplements.

Other factors that affect your PSA level include:

During treatment for prostate cancer, the PSA test is often performed at intervals to look for a falling level, which should be very low or undetectable by the end of treatment. Then your doctor continues to monitor it as a rise may indicate a cancer recurrence.

Why Men With Prostate Cancer Have Problems With Urination

To understand why men with prostate cancer often have urination problems, it helps to understand the anatomy of the prostate. The prostate is a small, walnut-shaped gland that has many functions in the male reproductive system. The urethra (the tube that allows urine to flow from the bladder to the outside of the body) is surrounded by the prostate. As the prostate enlarges as cancer advances, it constricts the urethra, causing difficulties with urination.

Regular medical checkups can help ensure you are being screened for prostate cancer and benign prostate enlargements. Prostate cancer is the second leading cause of cancer death in men. Don't skip your checkups.


PSA, Lab Tests Online, American Association for Clinical Chemistry, December 16, 2015.

Prostate-specific antigen (PSA) blood test, MedlinePlus, U.S. National Library of Medicine. 2/2/2015.

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