Short answer: PSA (prostate-specific antigen) is a protein made by the prostate gland, and the blood test measures how much of it circulates. A raised PSA can come from prostate cancer, but also from an enlarged prostate, inflammation or infection, recent ejaculation, cycling or a recent prostate examination. Whether and when to test is a decision men make with their doctor.
At a glance
| Measures | Prostate-specific antigen in the blood |
|---|---|
| Units | ng/mL (µg/L) |
| LOINC | 2857-1 |
| Raised by | Cancer, but also enlargement, inflammation, infection, ejaculation, cycling, examination |
| Variants | Free PSA, PSA density, PSA velocity; read by the doctor together |
| Keep | Each value with the date; the change over time matters as much as the level |
What the test measures
PSA is reported in ng/mL (µg/L, the same number). Some labs also measure free PSA and give the ratio of free to total PSA, which doctors sometimes use to decide on next steps.
Because PSA varies for many reasons, doctors often look at how it changes over time and repeat a raised result before acting. Medicines for an enlarged prostate (5-alpha-reductase inhibitors) lower PSA, so they must be taken into account.
When it is ordered
Common reasons, which your doctor adapts to you:
- after discussing the benefits and harms of testing with a doctor (screening policies differ between countries);
- to follow a known prostate condition or after treatment.
How the result is written on the report
| Result on the report | LOINC code | Usual unit | Also seen as |
|---|---|---|---|
| Prostate specific Ag (PSA), serum or plasma | 2857-1 | ng/mL | µg/L (same number) |
PSA in ng/mL and µg/L is the same number. Results from different assays can differ slightly, which is one reason to use the same laboratory when following PSA over years.
Reading your report
The NHS advises avoiding ejaculation and vigorous exercise such as cycling for 48 hours before the test. Tell your doctor about any recent urinary infection or prostate examination. The decision on what a result means, and on further tests, belongs to your doctor; a PSA history in one place makes that conversation easier.
Keeping the results in your record
Scan or photograph the report in Anpheros Daily: each value is read with its unit and the laboratory's reference range, you check it, and it is stored with its LOINC code as an HL7 FHIR Observation, a format used by many hospitals and national health systems. Results from different laboratories line up on one chart over time, and the lab unit converter helps when two reports use different units. Our guide on how to read lab results explains reference ranges and flags in general; the lab results guide for a new doctor shows how to share them.
What this page does not do
It explains what the test is and how the result is written. It does not interpret your result, diagnose or recommend treatment: the meaning of a value depends on your history, your other results and how the sample was taken, and that is your doctor's job.
Related pages
Sources
Frequently asked questions
Does a high PSA mean prostate cancer?
No. An enlarged prostate, inflammation, infection and other things also raise PSA. Further assessment is decided by a doctor.
Is ng/mL the same as µg/L for PSA?
Yes, it is the same number.
What can affect a PSA result?
Recent ejaculation, cycling, a urinary infection, a prostate examination and some medicines. Tell your doctor before the test.
Why does the trend matter?
Because PSA varies; a change over several results tells your doctor more than one value.
Try it in Anpheros Daily
Photograph your lab report and Anpheros Daily lines up each value with its reference range, so you can compare reports from different laboratories.
How it works in the app →
Anpheros builds a medical record that the patient controls and can share with any clinic, on an HL7 FHIR R4 platform, based in the EU. These guides help you understand and organise your health; they do not replace your doctor.
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