PSA blood test: what it measures and what your result means

Medically reviewed by Dr Lebeth Jacob · 21 October 2026

Quick answer: PSA (prostate-specific antigen) is a protein made by the prostate gland. A PSA blood test measures how much is in your blood. A raised level can be a sign of prostate cancer, but it is more often caused by an enlarged prostate, infection or recent activity. PSA can't diagnose cancer on its own, so a raised result leads to further checks.

What is PSA?

The prostate is a small gland below the bladder in men. It makes PSA, which helps keep semen runny. A small amount leaks into the blood, and that amount tends to go up when the prostate is larger, inflamed or irritated.

PSA naturally rises with age as the prostate grows. That's why the level that leads a doctor to suggest more tests is higher for older men.

Why is PSA tested?

  • You are over 50 and want to check your prostate health
  • You are Black, or your father or brother had prostate cancer, which raises your risk from your mid-40s
  • You have symptoms such as needing to pee more often, especially at night, or a weak flow
  • You have had a raised PSA before and want to check whether it has changed
  • You are being monitored after prostate treatment

There is no national PSA screening programme in the UK. Men over 50 can ask their GP for a test after talking through its pros and cons.

What does a high PSA result mean?

A raised PSA means something is affecting your prostate, but most men with a raised level do not have cancer. Cancer Research UK says around 72 to 80 in every 100 men with a raised PSA do not have prostate cancer. Common reasons are:

  • An enlarged prostate (benign prostatic hyperplasia), which is very common with age
  • Inflammation or infection of the prostate (prostatitis)
  • A urine infection
  • Ejaculation or vigorous exercise, especially cycling, in the past two days
  • A recent prostate examination, biopsy or catheter
  • Prostate cancer

A GP will usually repeat the test and may examine the prostate. If PSA stays raised, the next step is often an MRI scan of the prostate.

Can PSA be low or normal with cancer?

Yes. The PSA test can miss some prostate cancers, so a normal result doesn't rule it out completely. If you have symptoms, see a GP even if your PSA is normal.

What can affect your result?

For the most reliable result, in the 48 hours before your test avoid:

  • Ejaculating
  • Vigorous exercise, including cycling

Also wait to test if:

  • You have a urine infection: wait until about six weeks after it has been treated
  • You've had a prostate biopsy in the past six weeks

Medicines for an enlarged prostate or hair loss, such as finasteride and dutasteride, lower PSA. Tell the doctor reviewing your result if you take them.

When to see a GP

Your results report shows the laboratory's normal range and flags any result outside it. Speak to your GP if:

  • Your PSA is flagged high, or has risen since a previous test
  • You need to pee more often or urgently, especially at night
  • You have a weak flow, difficulty starting, or feel your bladder hasn't fully emptied
  • You notice blood in your urine or semen

Go to A&E if you suddenly can't pee at all.

How we test PSA

You can have PSA tested with a blood sample taken at one of our 250+ partner clinics, or with a finger-prick kit at home. Samples are analysed by a UKAS-accredited laboratory. Results are usually ready in 3–5 working days, with a doctor's comments on every result.

Tests that include PSA

Prices for in-clinic tests include your appointment. Compare every test with PSA in the biomarker explorer

Frequently asked questions

What is a dangerous PSA level?

No single PSA level means cancer, and none rules it out. The higher the level, the more likely it is that a doctor will suggest an MRI scan. Any result flagged high should be discussed with your GP, along with your age and symptoms.

What is a normal PSA level by age?

PSA rises naturally with age, so the level that's considered raised is higher for older men. Your report flags your result against the laboratory's range, and your GP takes your age into account when deciding what to do next.

What should I not do before a PSA test?

Avoid ejaculating and vigorous exercise, especially cycling, for 48 hours before. Don't test while you have a urine infection, or within six weeks of a prostate biopsy.

Does a high PSA mean I have cancer?

Usually not. Most raised results are caused by an enlarged prostate, inflammation or infection. Further checks, usually starting with a repeat test and an MRI scan, are needed to find out.

How often should I have a PSA test?

There is no set schedule for men without symptoms. Many men who choose to test do so every one to two years after 50, or from 45 if they're at higher risk. If your PSA has been raised before, follow your doctor's advice on when to retest.

What is free PSA?

PSA travels in the blood either attached to proteins or on its own (free). Some tests measure both. The share that's free can help a doctor judge what a raised total PSA is likely to mean.