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The PSA test is a blood test that measures the amount of prostate specific antigen (PSA) in your blood. It can help to diagnose prostate cancer.
Your doctor or nurse takes a sample of your blood. This can be done at your GP practice. They then send this off to a laboratory to check the amount of PSA.
When you have the test
You might have a PSA test if you:
- have symptoms that could be caused by prostate cancer
- are aged 50 and over and have asked your GP for a test
Doctors also check your PSA level as you go through prostate cancer treatment. It helps them see how well treatment is working.
What is PSA?
Prostate specific antigen (PSA) is a protein produced by both normal and cancerous prostate cells. It’s normal for all men to have some PSA in their blood.
A high level of PSA can be a sign of cancer. But your PSA level can also be raised in prostate conditions that are not cancer. For example, if you have a urine infection.
A diagnosis of prostate cancer is not made on a PSA level alone.
Discussing the test
Your doctor should explain the possible risks and benefits of having a PSA test.
The PSA level isn’t a reliable sign of whether a man has prostate cancer. Some men have prostate cancer but have a PSA level that is normal for their age. Other men have a higher PSA level but don’t have prostate cancer.
Your doctor should discuss the test with you and give you enough time to talk about it with your partner or family.
Understanding your PSA test results
PSA is usually measured in nanograms per millilitre of blood (ng/ml). There is no single PSA reading that is considered normal. The reading varies from man to man and the level increases as you get older. Typically, most men have a PSA level of less than 3ng/ml.
Your doctor may refer you to a specialist if your PSA level is over what is consider normal for your age. It’s important to remember that a PSA level higher than 3ng/ml may be normal in older men. Talk to your doctor about your PSA level and what this means for you.
Doctors usually follow guidelines that advise when to refer someone to a specialist. These guidelines vary slightly between the different UK nations. It’s important to know that your doctor also uses their own experience and judgment when deciding who needs to see a specialist.
Your doctor may refer you to a specialist if your PSA level is:
Your doctor uses their own judgement if you are aged below 40 or above 79.
If you are referred to a specialist, they may do a physical examination and check for any other symptoms you might have. You may then have other tests such as an MRI scan and a biopsy 
.
What affects the PSA level?
The PSA level can change due to things other than cancer.
Your doctor might want to rule out a urine infection before carrying out a test. If you’ve had a urine infection, you shouldn’t have a PSA test for at least 6 weeks.
Other things that affect your PSA level include:
- ejaculation within the last 48 hours
- having an examination of your prostate (digital rectal examination) before the PSA blood test
- doing vigorous exercise within the last 48 hours
- having had a prostate biopsy in the last 6 weeks
There are different guidelines about how long you should wait between these activities and having a PSA test. Ask your doctor what they recommend.
Free and bound PSA
PSA has different forms. It can be:
- bound – attached to other proteins in the blood
- free – not attached to proteins
The standard PSA test measures the amount of free and bound PSA in the blood.
Screening
There is no national screening programme for prostate cancer in the UK. This is because previous research showed that the PSA test isn’t a reliable test that can pick up prostate cancer that needs treatment. Research is going on to find a new test. Or to see if the current test is more effective if used in a different way.
If you’re over 50 and want to have a PSA test, you can ask your GP. There are possible risks to having this test that your doctor can discuss with you. They will help you make a decision about whether to have the test.
