Prostate Cancer London

A raised PSA is not a diagnosis

First, take a deep breath. The majority of men who walk into our clinic with a raised PSA do not have prostate cancer. Here is what the number really means, and what a sensible next step looks like.

Written and reviewed by Mr Ashwin Sridhar, Consultant Urological Surgeon

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The basics

What PSA actually is

PSA stands for prostate-specific antigen. Notice the name: it is specific to the prostate, not specific to cancer.

Think of PSA as a protein manufactured naturally by every cell in your prostate gland. Under normal circumstances, most of it stays inside the prostate fluid, with only a tiny trickle leaking into your bloodstream. Anything that enlarges the prostate, irritates it, stretches it, or inflames it will cause more of this protein to spill over into the blood.

Which means a raised reading is a signal, not an answer.

PSA is not a "cancer test". It is simply a sensitive smoke detector. It tells us that something is stirring the prostate gland, but it cannot tell us whether that smoke is coming from a harmless bonfire (benign enlargement), steam from a kettle (infection or exercise), or an actual fire (cancer).

This is exactly why we do not jump straight to invasive biopsies based on a single blood test. Instead, we pair your PSA with a multiparametric MRI scan to look directly at the tissue, and we calculate your PSA density by dividing your PSA number by your exact prostate size. If the volume explains the number and the scan is clear, you have your answer without unnecessary fear or intervention.

Six common causes

Harmless reasons your PSA can be raised

These are the most common, completely harmless reasons your PSA might be elevated.

Natural ageing and prostate size (BPH)
As you get older, the normal, benign prostate tissue naturally grows. A prostate the size of a plum simply has more cells and makes more PSA than a prostate the size of a walnut. A reading of 5.5 might sound concerning in isolation, but if you have a large 80 gram prostate, that number could be completely normal for your anatomy.
Urinary or prostate infections (prostatitis)
If bacteria enter the urinary tract or prostate, the tissue becomes inflamed. That acute inflammation breaks the natural barrier, allowing PSA to pour into the bloodstream. A simple, temporary infection can easily send a PSA into double digits.
Recent ejaculation
Sexual activity and ejaculation cause the prostate to contract and expel fluid. In doing so, extra PSA temporarily leaks into the circulation. Having sex within 48 hours before a blood draw can artificially bump your number.
Vigorous exercise and cycling
Sitting firmly on a narrow bicycle saddle puts direct mechanical pressure on the prostate, essentially bruising or stimulating the gland. Heavy cycling in the days leading up to a test frequently produces a false spike.
Recent examinations or procedures
A recent catheter insertion, a cystoscopy (camera test), or even a vigorous digital rectal examination done right before a blood sample can temporarily push the PSA upward.
Urinary retention
If you have struggled to empty your bladder and urine has backed up, the increased pressure against the prostate elevates PSA.

How it is read

How a specialist reads the number

When we look at your PSA result, we never treat it like a simple pass-or-fail exam. Looking at one isolated number without context causes a huge amount of unnecessary panic. Here is how we make sense of what your number actually means for you.

  1. We always double-check before acting

    Your PSA level can bounce up and down naturally from week to week by as much as 20% to 30%. If your number comes back slightly higher than expected, the very first thing we do is repeat the test a few weeks later. We make sure you have not ejaculated, cycled, or had a urine infection in the 48 hours beforehand. If it was just a temporary spike, the second test often settles right back down.

  2. Matching the number to your prostate size

    This is the most powerful tool we have. Think of your prostate like an engine: a small Mini Cooper engine should produce a small amount of exhaust; a large lorry engine will naturally produce much more. When we do your MRI scan, we measure the exact size of your prostate in cubic centimetres, then divide your PSA number by that size to get your PSA density. If your PSA is 6.0 but your MRI shows a large, benign prostate of 70cc, your density is very low, under 0.10, and the size of the gland completely explains the number. If your PSA is 6.0 but your prostate is tiny, say 20cc, that little gland is producing far more PSA than it should, and we need to look much more closely even though the absolute number did not seem sky-high.

    The same PSA reading on two different prostatesA PSA of 6.0 measured against a large 70cc prostate gives a low density, and the number is explained by the size of the gland. The same PSA of 6.0 measured against a small 20cc prostate gives a higher density and is worth a closer look.PSA 6.070ccprostateLow densityExplained by the size of the glandPSA 6.020ccprostateHigher densityWorth a closer look
    Same blood result, two different meanings. The MRI is what supplies the gland volume.

  3. Free versus bound PSA

    In your blood, PSA travels in two ways: either floating freely on its own, or locked onto blood proteins. Normal, benign prostate enlargement mostly releases free PSA, while cancer cells tend to release PSA that gets locked onto proteins. If your PSA is in that tricky grey zone between 4 and 10, we measure how much of it is free floating. If more than 25% is free, it strongly suggests harmless enlargement. If less than 10% is free, it nudges us toward doing a targeted check.

  4. The speed of change

    Where your PSA is heading over time matters far more than where it sits on a single day. If a PSA shoots up from 2.5 to 12.0 in three weeks, that is almost certainly an acute infection or inflammation. Cancer does not jump like that overnight. If your PSA creeps up gradually year after year, say from 2.0 to 3.2 to 4.8 over two years, that steady upward curve tells us something is slowly developing and warrants a scan.

The decision

Who needs an MRI, and who does not

We do not use MRI as a generic screening test for every man who walks through the door. We use it as a precision diagnostic tool when there is a clear biological signal that something needs investigating.

When an MRI genuinely helps

In our practice, a PSA above 3 that a repeat test confirms earns a scan, which follows the national guidance the NHS works to. It earns its place when the prostate feels uneven, unusually firm, or has a small lump during examination, even if your PSA reading is low. It earns its place when your PSA has crept consistently higher over two or three checks across the last year or two, and when you have a father or brother diagnosed under 60 or carry genes like BRCA2, and your PSA is sitting on the higher side of normal.

When you genuinely do not need one

You are 55, your PSA is 1.1, your physical examination is smooth, and there is no heavy family history. Your risk of clinically significant cancer is microscopic. Or you are waking once or twice at night and your stream is slightly slower, but your PSA is completely normal. Those are everyday signs of a harmless enlarged prostate that need simple symptom support, not imaging. Or your PSA jumped after a urine infection. The answer there is letting the tissue heal and re-checking the blood, not scanning an irritated gland.

What we say to the man whose tests are clear, but who still wants an MRI

We completely understand why you are asking for an MRI today. When you are worried about your health, it is natural to want the most advanced scan possible to walk away with 100% peace of mind. If we thought you needed a scan, we would order it immediately. But right now, your blood tests are reassuring, your physical examination is healthy, and your risk is minimal. Having an MRI when you do not need one can actually create anxiety rather than fix it.

MRI scanners are so powerful that they pick up completely harmless things: tiny cysts, old scar tissue from a past infection, or normal benign lumps. If a scan highlights one of those as an indeterminate shadow, you are suddenly thrown into weeks of worry. That innocent shadow often triggers extra tests, including needle biopsies that carry risks of pain, bleeding and infection, all to investigate something that was never going to bother you. And a clear scan today is not a lifetime pass. Your body continues to change naturally as you get older.

The safest, smartest approach is to bank your healthy numbers today as your personal baseline. We repeat a simple PSA blood test in 12 to 24 months. If your numbers ever start to tick upward, we step in with an MRI straight away. You are safe, you are fully checked, and we have a clear, proactive plan to keep you protected. And if despite all that you would still like an MRI, we can arrange the scan after a proper discussion about what it might show.

One last note

The mildly raised, stable PSA

As long as your PSA is stable over serial measurements, a mildly elevated PSA could simply be normal for you and does not need further tests. A baseline MRI is not a bad idea in this setting, but serial MRIs are not necessary provided the PSA stays stable.

Written and medically reviewed

Mr Ashwin Sridhar, Consultant Urological Surgeon

Last reviewed 1 September 2026.

Other guides worth reading

Questions men ask at this moment

The questions that come up most often once a PSA result lands.

We know it feels like paying for the scan is the safest, most thorough thing to do. But medical tests are not like buying extra travel insurance; they carry real downsides if you do not need them. Modern MRI scanners are so powerful that they find tiny, innocent imperfections in almost everyone. If we scan a healthy prostate and see a harmless little smudge, we cannot just un-see it. We then have to discuss putting biopsy needles into you to prove it is harmless. Paying for a scan that turns a healthy man into an anxious patient having an unnecessary procedure is not good medicine. If your numbers or examination ever change, we will be the first to order the scan.
It is completely understandable that hearing a story like that shakes your confidence. Those cases are what we call outliers. They are rare, which is why people talk about them. In almost all of those situations, if you look closer, there was usually another clue: maybe his PSA was climbing over time, or his prostate felt abnormal when examined, or he had a strong family history. In medicine, we do not subject millions of men to high-tech imaging based on the rarest 1% exception when all their standard markers are totally reassuring. If your baseline numbers, examination and family background are clear, your risk is exceedingly low. We can still discuss organising a scan if you have a strong preference for it and understand what it might show.
Simply having this assessment has zero physical impact on your erections, your libido or your sex life. The only thing that can affect your erections at this stage is stress and anxiety. If we ever did find something down the road that required treatment, modern robotic surgery and targeted therapies are specifically designed around nerve-sparing techniques to preserve sexual function. But right now, you are only having a check-up.
Neither of those things will happen, so please do not worry. The digital rectal examination takes under 30 seconds. It feels a little unusual and can give you a brief sensation that you need to pass urine for three or four seconds while the gland is felt, but as soon as the finger is removed, that feeling disappears completely. It does not cause bladder leakage, it does not cause erections, and it causes minimal discomfort.
Almost certainly not. This is the single biggest misconception men have: assuming urinary symptoms equal prostate cancer. Early, curable prostate cancer sits silently on the outer shell of the prostate and causes zero symptoms. What is waking you up at night is the natural, completely benign enlargement of the inner part of the prostate (BPH) that happens to every man as he gets older. It squeezes the water pipe like a kinked garden hose. It is an annoyance that we can easily treat with simple tablets, but it is not a sign of cancer. It could also be a host of other medical issues that make you pass urine more at night.
Not at all. The number 4.5 is just a concentration measurement. It means 4.5 nanograms of protein per millilitre of blood. It is not a percentage, not a stage, and not a cancer score. A man with a PSA of 4.5 could have a completely benign, large prostate, while a man with a PSA of 1.5 could occasionally have an issue. It is a general biological indicator, which is why we pair it with gland size to calculate your density.
No, you are definitely not guaranteed to get it. Having a first-degree relative, like a father or brother, diagnosed with prostate cancer does double your lifetime statistical risk compared to a man with no family history, but that is a probability, not a certainty. It simply means you are a man who should start proactive PSA checks in your 40s rather than waiting until your 50s. If your tests today are normal, having a father who had it does not change the fact that you are healthy right now.
Prostate cancer is typically one of the slowest-moving conditions in the human body. It develops over years, not weeks or months. Aggressive cancers almost always announce themselves early with a clear biological signal, a sharp spike in PSA or a distinct lump on examination. Because your PSA is low and your exam is clear today, you do not have an aggressive, hidden tumour silently spreading. Waiting 12 months for a routine repeat blood test is completely safe and standard international best practice.
You do not need to go on an extreme diet. No scientific study has ever shown that eliminating sugar or dairy shrinks the prostate or cures cancer. What genuinely helps prostate and overall vascular health is everyday common sense: a balanced Mediterranean-style diet, staying physically active, keeping your weight in a healthy range, and moderating alcohol. Living on kale smoothies will not change your PSA, so enjoy your meals and do not add dietary stress to your life.
You are completely clear today, which is fantastic news. But it is a snapshot, not a lifetime warranty. Because your prostate will continue to produce cells and grow naturally as you age through your 50s, 60s and 70s, your risk profile changes over time. That is why we do not say goodbye forever. We put a simple, non-invasive check on the calendar every 12 to 24 months to make sure your numbers remain steady.

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