PSA (prostate-specific antigen) test: what it means
What it measures
The PSA test is a blood test that measures the level of prostate-specific antigen (PSA), a protein made by the prostate, in a sample of your blood. A small amount of PSA normally circulates in the blood.
Why it’s ordered
It is used to screen for prostate cancer and to help evaluate the cause of prostate conditions that are not cancer. A provider may also order it if the prostate feels abnormal on exam, and to monitor people during or after prostate cancer treatment; a screening test cannot by itself diagnose cancer, so further tests are needed if it finds a possible sign.
General reference range
There is no single universally "normal" or "abnormal" PSA level. MedlinePlus notes that a level up to about 4.0 ng/mL has traditionally been considered normal, but this varies by age (PSA is often lower in men in their 50s and younger and tends to be slightly higher in older men). These figures are general reference points only and can differ by laboratory, age, sex, and testing method — your own lab report and its stated reference range are what apply to you. A number on its own is not a diagnosis.
If it’s high
A higher-than-expected PSA is not proof of cancer; the test cannot tell the difference between cancer and noncancerous causes. In general, the higher the level, the greater the chance that cancer is present, but higher PSA may also be seen with an enlarged prostate (benign prostatic hyperplasia, or BPH); prostatitis (inflammation of the prostate); a urinary tract infection; certain medicines; and temporary causes such as recent ejaculation or intercourse, a recently placed catheter, or recent procedures involving the bladder or prostate (for example cystoscopy or biopsy). This is a general, not complete, list of possible associations, and it is possible to have a high PSA without prostate cancer.
If it’s low
A low PSA is generally considered reassuring, and MedlinePlus does not describe low PSA as a distinct concern or typically report it as an abnormal "low" result. However, MedlinePlus notes it is possible (uncommonly) to have a low PSA and still have prostate cancer, which is one reason results are always interpreted in context rather than by the number alone.
A result is not a diagnosis
Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.
Medicines that can move this result
Finasteride blocks the enzyme that converts testosterone into DHT, the hormone that drives prostate growth, so the gland shrinks and releases about half as much PSA. The label instructs that after six months or more of treatment a PSA value should be doubled before it is compared with the normal range for untreated men.
Source ↗Dutasteride works like finasteride but blocks both forms of that enzyme, and the label reports serum PSA falling by roughly half within the first 3 to 6 months of treatment.
Source ↗Testosterone is the hormone prostate tissue runs on, so replacing it can stimulate the gland and push PSA up. The label recommends periodic PSA testing during treatment for exactly this reason.
Source ↗Leuprolide suppresses the body's testosterone production, and with far less hormone to stimulate it the prostate releases much less PSA. In a study of 1,273 men treated for advanced prostate cancer, median PSA fell 94% — from 11.6 to 0.7 ng/mL — over the first six months, so a very large drop on this drug is the expected treatment response rather than a lab error.
Source ↗Do not stop a prescribed medicine over a lab number. These are recognised associations, not a finding about your result — your value may have nothing to do with any medicine you take, and the list is not complete. Bring it to whoever prescribed the drug; they can weigh it against why you are taking it.
Frequently asked
- What does the PSA (prostate-specific antigen) test measure?
- The PSA test is a blood test that measures the level of prostate-specific antigen (PSA), a protein made by the prostate, in a sample of your blood. A small amount of PSA normally circulates in the blood.
- What is a normal PSA (prostate-specific antigen) test range?
- There is no single universally "normal" or "abnormal" PSA level. MedlinePlus notes that a level up to about 4.0 ng/mL has traditionally been considered normal, but this varies by age (PSA is often lower in men in their 50s and younger and tends to be slightly higher in older men). These figures are general reference points only and can differ by laboratory, age, sex, and testing method — your own lab report and its stated reference range are what apply to you. A number on its own is not a diagnosis.
- What does a high result mean?
- A higher-than-expected PSA is not proof of cancer; the test cannot tell the difference between cancer and noncancerous causes. In general, the higher the level, the greater the chance that cancer is present, but higher PSA may also be seen with an enlarged prostate (benign prostatic hyperplasia, or BPH); prostatitis (inflammation of the prostate); a urinary tract infection; certain medicines; and temporary causes such as recent ejaculation or intercourse, a recently placed catheter, or recent procedures involving the bladder or prostate (for example cystoscopy or biopsy). This is a general, not complete, list of possible associations, and it is possible to have a high PSA without prostate cancer.
- What does a low result mean?
- A low PSA is generally considered reassuring, and MedlinePlus does not describe low PSA as a distinct concern or typically report it as an abnormal "low" result. However, MedlinePlus notes it is possible (uncommonly) to have a low PSA and still have prostate cancer, which is one reason results are always interpreted in context rather than by the number alone.
Other lab tests
Sources
General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.