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Biomarker library / Cancer screening

PSA (prostate-specific antigen) (PSA)

Also called prostate specific antigen test

PSA is a protein made by the prostate. The blood level rises with prostate cancer, but also with benign enlargement, inflammation and recent mechanical stimulation, which is exactly why interpreting it is hard.

Written by the VitalDecades editorial team Reviewed by the editorial review process Updated

01  /  Reference ranges

What counts as normal

Scale in ng/mL. Cut points from the sources listed below.
Population Men
Category Traditionally considered not elevated
Range under 4 ng/mL NCI: no single threshold separates normal from abnormal; age-adjusted cutoffs run about 2.5 (younger men) to 5 (older men).
Source National Cancer Institute, Prostate-Specific Antigen (PSA) Test fact sheet

Effective

Population Men
Category Traditionally abnormal; prompts evaluation
Range 4 or higher ng/mL Usually repeated first. Infection, benign enlargement and recent stimulation all raise PSA without cancer.
Source National Cancer Institute, Prostate-Specific Antigen (PSA) Test fact sheet

Effective

Normal vs optimal

We print the traditional threshold because you will meet it on lab reports, not because it is a diagnosis. A PSA of 4.5 in a 70-year-old with an enlarged prostate and a PSA of 2.8 that doubled in a year are very different results; only one of them is above 4.0.

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02  /  Why it matters

What the number tells you

The NCI's fact sheet is blunt: there is no single threshold that distinguishes a normal from an abnormal PSA, in part because no specific level means someone has prostate cancer. Traditionally a value above 4.0 ng/mL was considered abnormal and could prompt a biopsy discussion, with clinicians often using lower cutoffs (around 2.5) for younger men and higher (around 5) for older men. The trend over time and the context matter more than one number.

03  /  In practice

Testing and what moves it

When it is tested

  • USPSTF (2018): for men 55 to 69, periodic PSA screening is an individual decision after discussing benefits and harms; for men 70 and older, the USPSTF recommends against PSA screening (this topic is under update).
  • Avoid testing within about 48 hours of ejaculation or vigorous cycling, and one to two months after a prostate procedure or infection, all of which raise PSA.
  • An elevated result is usually repeated before anything else happens.

What raises it

  • Prostate cancer, benign prostatic enlargement, prostatitis and urinary infection.
  • Transiently: ejaculation, vigorous cycling, recent biopsy or catheterization (per NCI, for one to two months).

What lowers it

  • 5-alpha-reductase inhibitors (finasteride, dutasteride) roughly halve PSA; tell whoever interprets the test.
  • Obesity dilutes PSA modestly.

04  /  Related

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Frequently asked questions

What is a normal PSA level by age?

There is no single normal. The NCI notes the traditional 4.0 ng/mL threshold, with clinicians often using roughly 2.5 for younger men and 5 for older men. Interpretation leans on your age, prostate size, medications and how the value is trending.

At what age should I get a PSA test?

The USPSTF's 2018 statement makes PSA screening an individual decision for men 55 to 69 after weighing benefits (small reduction in prostate-cancer death) against harms (false positives, biopsies, overdiagnosis), and recommends against it at 70 and older. Higher-risk men, including Black men and those with a family history, may reasonably start that conversation earlier; the topic is currently being updated.

Can I do anything before the blood draw to avoid a false high?

Skip ejaculation and vigorous cycling for about 48 hours, and do not test within one to two months of a urinary infection, prostate procedure or biopsy.