Prostate-Specific Antigen (PSA) Blood Test

Prostate-specific antigen (PSA) is an enzyme produced by the prostate gland. Normally, PSA is secreted in small amounts into the bloodstream. However, larger amounts of PSA are released when the prostate gland is enlarged, infected, or diseased. The level of PSA in the blood can be determined by a simple blood test.

Why Do I Need a PSA Test?

The PSA test is the most effective test currently available for the early detection of prostate cancer. PSA testing and the digital rectal examination (DRE) are crucial in detecting prostate cancer in its early stages, when it usually produces no physical symptoms. PSA testing is also used to monitor the progress of prostate cancer which has already been diagnosed.

What Is Considered a Normal PSA Blood Level?

PSA blood test results are reported as nanograms per milliliter, or ng/ml. Normal levels usually range from 0 ng/ml to 4 ng/ml, although what is considered normal may vary by age and race. Mild to moderate increases in PSA — between 4 and 10 — are considered borderline, while levels over 10 are considered high. The higher the PSA, the more likely the presence of prostate cancer.

Does Normal PSA Vary with Age?

Mayo Clinic study determined that since benign prostatic hyperplasia (BPH) yields higher PSAs than the normal level of 4.0 ng/ml, older men will more likely have higher normal PSAs than younger men.

Age PSA Level (ng/ml)
40-49 2.5
50-59 3.5
60-69 4.5
70-79 6.5

Does Normal PSA Vary by Race?

Studies have shown that African American men, with and without prostate cancer, have higher PSA levels than other racial groups. African American men in their 50s and 60s, without cancer, have average PSA levels approximately one point higher than their Caucasian counterparts. The reasons for this are still under investigation.

What Is Free-to-Total PSA?

Some PSA binds with other proteins in the blood, while other PSA circulates alone, or "free" in the bloodstream. The free-to-total PSA test compares the amount of free PSA to total PSA — both free and bound — in the blood. Free PSA is associated with benign conditions; bound PSA is associated with malignancy. A low percentage of free PSA (25 percent or less) means a greater likelihood of prostate cancer than higher percentages of free PSA.

How Often Do I Need a PSA Test?

The American Cancer Society recommends annual PSA testing for:

  • Men 50 and older with a life expectancy of at least 10 years.
  • Men over 40 with blood relatives who have had prostate cancer.
  • Men over 40 who are in high-risk groups, such as African Americans.

The Prostate Cancer pages of this website are part of the Comprehensive Prostate Cancer Awareness Program (CPCAP), a major regional effort to reduce the rates of death and illness caused by prostate cancer in southwestern Pennsylvania. Funding for CPCAP is provided by a grant from the Commonwealth of Pennsylvania.