PSA (Prostate-Specific Antigen)
PSA is a protein produced almost exclusively by prostate gland cells. It is released into blood in small amounts from a normal prostate and in larger amounts when the prostate is enlarged, inflamed, or cancerous. PSA is used for prostate cancer screening (controversially, because it has limited specificity), for monitoring men treated for prostate cancer, and for evaluating urinary symptoms in men over 50.
Reference Ranges
Male
0 – 4
ng/mL
Female
0 – 0.1
ng/mL
Child
Consult pediatrician
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
A PSA below 4 ng/mL is generally considered normal, though lower age-specific cutoffs (below 2.5 ng/mL under age 60) are increasingly used. Low PSA does not completely rule out prostate cancer — about 15% of clinically significant prostate cancers occur with PSA in the normal range.
What High Levels Mean
PSA between 4–10 ng/mL is the 'diagnostic gray zone' — prostate cancer risk is about 25%, but benign prostatic hyperplasia and prostatitis also commonly cause this range. PSA above 10 ng/mL carries about 50% cancer risk. Trends matter — PSA velocity above 0.75 ng/mL per year or a doubling time under 3 years raises concern regardless of absolute value.
Frequently Asked Questions
Should all men get a PSA test?
Routine PSA screening is controversial. Major guidelines recommend shared decision-making: men aged 55–69 with at least a 10-year life expectancy should discuss the pros and cons with their doctor before testing. Men at high risk (family history of prostate cancer, African ancestry) may start earlier at age 45. Screening beyond age 70 is generally not recommended.
What can raise PSA besides cancer?
Benign prostatic hyperplasia (very common after 50), prostatitis, recent ejaculation (within 48 hours), recent prostate exam, cycling, urinary catheterization, and recent prostate biopsy all raise PSA. Medications like finasteride roughly halve PSA — in men on finasteride, double the reported value to compare to standard cutoffs.
What is free PSA and when is it useful?
PSA exists in blood in free form and bound to proteins. The free PSA percentage (free/total × 100) helps distinguish cancer from benign enlargement in the 4–10 ng/mL range. A low free-PSA percentage (below 10%) increases cancer likelihood; a high free-PSA percentage (above 25%) suggests benign enlargement. Free PSA is most useful when total PSA is in the gray zone.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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