What is PSA?

PSA or Prostate Specific Antigen is a protein produced by the prostate found mostly in the semen with very small amounts released into the bloodstream. When there’s a problem with the prostate—like the development and growth of prostate cancer—more and more PSA is released. It 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.

What Do the Numbers Mean?

  • Levels under 4 ng/mL are usually considered “normal.”
  • Levels over 10 ng/mL are usually considered “high”
  • Levels between 4 and 10 ng/mL are usually considered “intermediate.”

When prostate cancer develops, the PSA level usually goes above 4. Still, a level below 4 does not guarantee that a man doesn’t have cancer. About 15% of men with a PSA below 4 will have prostate cancer on a biopsy.


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PSA is not a perfect test. Levels can be elevated if other prostate problems are present, such as BPH or prostatitis. Some men with prostate cancer may even have low levels of PSA. PSA can also be diluted in men who are overweight or obese, due to a larger blood volume, and a Biopsy at a relatively lower number (i.e. 3.5 instead of 4) should be considered.

What Happens if my PSA is High?

If your PSA level is high, your doctor may advise either waiting a while and repeating the test, or getting a prostate biopsy to find out if you have cancer.

Some doctors use different PSA cutoff points in the decision to do a prostate biopsy. Some may advise biopsy at a PSA of 4 or higher, and some may recommend it at 2.5 or 3.  In addition, there are many factors that play into a decision to do a prostate biopsy besides PSA, including your age, race, and family history.  Talk to your doctor to find out what is recommended for you.

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