Understanding PSA Tests: Your Complete Guide to Prostate Health
If your GP has ordered a PSA test, or you have a result in front of you and are trying to work out whether the number is a problem, this article is for you.
The short version: a PSA result is not a diagnosis. It is one input, and on its own it tells you remarkably little. What matters is the number in context — your age, your prostate, what medications you are on, what your previous results were, and what an examination shows. A single figure read in isolation causes a great deal of unnecessary alarm, and occasionally false reassurance.
What PSA is, and what it isn't
Prostate-specific antigen is a protein produced by prostate cells — both healthy ones and cancerous ones. It has a normal job: it helps liquefy semen. A small amount circulates in the blood, and that is what the test measures, reported in nanograms per millilitre.
The critical point is in that first sentence. Healthy prostate cells produce PSA too. So a raised PSA tells you there is more prostate activity than expected. It does not tell you why.
PSA is not a cancer test. It is a prompt to look further.
When testing should start
For most men, the conversation starts at 50, and testing every two years from there.
If you have a family history of prostate cancer, it starts earlier — somewhere between 40 and 45, depending on how close the relative is and how many there are. A father or brother with prostate cancer moves the starting point more than a more distant relative.
Other factors can shift when testing should start. If you are unsure whether any apply to you, it is worth raising with your GP — or bringing to a consultation, where it can be worked through against your own history.
After 70, testing is not automatic and it is not simply stopped either. It depends on your general health rather than your age. The question worth asking is whether finding a prostate cancer would actually change what happens next — because many prostate cancers grow slowly enough that, in a man with other significant health problems, finding one may cause more disruption than it prevents. In a man of 72 who is otherwise well and active, continuing to test usually makes sense.
That is a conversation to have with your GP or urologist rather than a rule.
The step that gets missed most often
Before any threshold below means anything, one question has to be answered: are you taking finasteride or dutasteride?
These medications — prescribed for prostate enlargement, and finasteride also for hair loss — halve PSA. A man on finasteride with a reported PSA of 2.8 has an effective PSA of 5.6. That is not a reassuring result. It meets the threshold for referral.
This is the single most commonly missed step in prostate assessment. If you take either medication, make sure whoever interprets your result knows, and make sure the doubling has been applied before anyone tells you the number is fine.
What counts as a result worth acting on
There is no universal "normal" PSA. What follows is the framework I use, and it depends on two tests rather than one — PSA fluctuates, and a single reading is a poor basis for a decision.
If you are under 70 with no particular risk factors, two tests taken one to three months apart showing either a PSA above 3.0 ng/mL with a free-to-total ratio under 25%, or a repeat PSA above 5.5 ng/mL, warrants specialist assessment.
If you are under 70 with a first-degree relative who has had prostate cancer, or a known BRCA1 or BRCA2 mutation, the threshold is lower: two tests one to three months apart above 2.0 ng/mL with a free-to-total ratio under 25%.
If you are 70 or over, two tests one to three months apart above 5.5 ng/mL with a free-to-total ratio under 25%.
Separately from all of this: if a rectal examination finds a hard or irregular prostate, that warrants assessment regardless of what the PSA says. A normal PSA does not override an abnormal examination.
The repeat test — and what to ask for
If your first PSA comes back above the level expected for your age, the next step is a second test one to three months later. That is not delay for its own sake. PSA moves, and confirming a result before acting on it prevents a great deal of unnecessary investigation.
Ask for the free-to-total ratio to be included on that second test. It is readily available and it genuinely changes the interpretation.
PSA circulates in two forms: free, and bound to proteins. A higher proportion of free PSA points toward benign enlargement. A lower proportion raises suspicion. This is why the thresholds above pair a number with a ratio rather than relying on the number alone — the same PSA of 4.0 means different things depending on that split.
Why your PSA might be raised without anything being wrong
Most raised PSA results are not cancer. Common explanations include:
Benign prostatic hyperplasia. The prostate enlarges with age in most men. More prostate tissue produces more PSA. This is by far the most common reason for a raised result.
Prostatitis or urinary infection. Inflammation raises PSA, sometimes substantially. If infection is present, it should be treated and the PSA repeated once it has cleared — testing during an active infection produces a number that means nothing.
Recent activity. Ejaculation within 24 to 48 hours, vigorous cycling, a recent rectal examination, or catheterisation can all lift a result. If any of these applies, mention it before anyone acts on the number.
Age itself. Baseline PSA rises gradually across a lifetime. This is expected, not pathological.
Bring the whole history, not the latest number
This matters more than most people realise. A PSA of 4.2 that has climbed from 1.8 over two years is a different clinical situation from a PSA that has sat stable at 4.2 for five years. Same number, different meaning.
If a PSA is rising quickly, that is relevant regardless of whether the absolute number has crossed a threshold. It is a supporting consideration rather than the main one — I would not act on a rate of change alone, but I would not ignore it either.
So bring every result you have, with its date. The trend is often more informative than the figure.
What happens after a raised result
The first step is the repeat test described above, with the free-to-total ratio.
Alongside that: a rectal examination, a review of your symptoms and medical history, a check for infection, and a look at what medications you are taking.
If those steps leave genuine concern, the next investigation is usually an MRI.
Where MRI fits
A multiparametric MRI is not a cancer diagnosis. It is a way of working out who genuinely needs a biopsy and who may reasonably avoid one — at least for now.
The scan is reported using a standardised score called PI-RADS, running from 1 to 5. A score of 1 or 2 means no suspicious lesion was identified, which is reassuring but does not end surveillance if your PSA remains raised. A score of 4 or 5 means a targeted biopsy is generally recommended. A score of 3 is the genuinely uncertain one, and what happens next depends on the wider picture rather than the scan alone.
A Medicare rebate is available for prostate MRI in defined circumstances, depending on your age and PSA level. Whether you qualify, and what any out-of-pocket cost would be, is worth confirming with the referring doctor and the imaging practice before the scan.
There is more detail on what the scan involves and how results are reported in MRI of the Prostate: What It Shows and What Happens Next.
If a biopsy is recommended
If imaging identifies a suspicious area, a targeted biopsy samples that area specifically, guided by the MRI images, rather than taking random samples across the gland as older techniques did. In most cases a small number of systematic samples are taken as well, so the whole prostate is assessed alongside the identified lesion.
What preparation involves is covered in Preparation for a Prostate Biopsy, and the procedure itself on the Prostate Biopsy page.
PSA after prostate surgery is a different question
If you have already had your prostate removed, the framework above does not apply to you. After surgery PSA should fall to undetectable, and the thresholds, the meaning of a rise, and what happens next are all different.
That is covered separately in PSA After Prostatectomy: What Your Number Means.
The reassurance worth holding onto
Most men with a raised PSA do not have prostate cancer. The number is a prompt to look properly, not a verdict — and looking properly means repeating the test with a free-to-total ratio, checking your medications, examining the prostate, and interpreting the result against your own history rather than a population average.
If you have a PSA result you are worried about, bring your full history of readings and any medications you take, and it can be looked at properly in context.
Contact the rooms if you would like to discuss a result.
Clinical note: This article provides general information and is not a substitute for individual medical advice. PSA results should be interpreted alongside your own history, examination and clinical circumstances.
Last reviewed: 22 August 2026
About the author: Dr Deanne Soares is a Melbourne-based urologist with a subspecialist focus in robotic prostate, kidney and bladder cancer surgery.
