Prostate-specific antigen (PSA) test

A blood sample is taken from a vein in your arm. To make sure your result is accurate, follow these guidelines before your test: 

• avoid ejaculation for 48 hours beforehand — this can temporarily raise PSA levels 
• avoid vigorous exercise that affects the prostate area, such as cycling, for 48 hours beforehand 
• have the blood test before any digital rectal examination (DRE) — or wait at least one week after a DRE — as pressure on the prostate raises PSA 
• wait at least six weeks after a prostate biopsy before having a PSA test 
• do not have the test if you have an active urinary tract infection, or within six weeks of one — infections can raise PSA significantly and for a prolonged period 
• tell your doctor about all medicines you are taking — some medicines, including finasteride, dutasteride, aspirin, statins, and certain chemotherapy drugs, can affect your PSA level

PSA is a protein produced mainly by cells in the prostate gland. Small amounts are normally present in the blood. A raised PSA level means the prostate is producing more PSA than usual — but this can happen for several reasons, not only cancer. 

In blood, PSA is found in two forms: some is ​‘free’ (not attached to other proteins) and some is ​‘complexed’ (bound to other proteins). Most PSA tests measure the total amount. A separate free PSA test can sometimes help assess the likelihood of cancer. 

The level that is considered raised varies with age. Laboratories therefore use age related normal ranges when reporting results. Your lab report will show the normal range used for your age group. 

A raised PSA has several possible causes: 

• Benign prostatic hyperplasia (BPH) — a non-cancerous enlargement of the prostate that is very common in older men. PSA levels between 2.0 and 10.0 ng/​mL are often caused by BPH rather than cancer 
• Prostatitis — inflammation or infection of the prostate, which can significantly raise PSA. PSA may remain raised for many months after a urinary tract infection 
• Prostate cancer — a PSA level above 10.0 ng/​mL may indicate a higher probability of prostate cancer, though your doctor will consider many other factors before referring you for further tests 

A raised PSA alone does not automatically lead to a biopsy or further investigation. Your doctor will weigh your PSA level against your prostate size, examination findings, age, ethnicity, family history, body weight, and any previous biopsy results.

If your total PSA is in the range of 2.0 to 10.0 ng/​mL, your doctor may also measure the free PSA ratio. This is the proportion of your total PSA that is not bound to proteins. 

A free PSA ratio above 25% suggests a lower probability of cancer. A lower ratio suggests a higher probability. This can help avoid unnecessary biopsies in some people.

Your doctor may also look at how your PSA is changing over time, or in relation to your prostate size: 

• PSA velocity — how quickly your PSA is rising. A faster rise over time may be more significant than a single raised result 
• PSA density — your PSA level relative to the size of your prostate (measured by ultrasound). Men with a larger prostate naturally produce more PSA, so a high PSA may be less concerning in someone with a known large prostate 
• PSA doubling time — how long it takes for your PSA to double. This is particularly used to monitor treatment and guide decisions about further therapy

A result within the normal range is reassuring but does not completely rule out prostate cancer. Around 15 in 100 men with a normal PSA do have the condition. If you have ongoing symptoms or other risk factors, your doctor may still recommend further tests.

A single raised PSA result does not automatically mean you will be referred for a biopsy. Your GP will consider your full picture — including symptoms, family history, ethnicity, examination findings, and any previous PSA results — before deciding on next steps. 

If further investigation is needed, you may be referred to a urologist. This may involve a multiparametric MRI (mpMRI) scan of the prostate, which is now commonly used before a biopsy to help identify where cancer is most likely to be and to reduce unnecessary biopsies. 

If you are diagnosed with prostate cancer, treatment options depend on the type and stage of cancer. Many prostate cancers are slow-growing, and active surveillance (careful monitoring without immediate treatment) may be recommended. Your specialist will work with you to find the right approach for you. Find out more at 

NHS: prostate cancer treatment

Several things can raise PSA temporarily or give a misleading result: 

• ejaculation within 48 hours before the test 
• vigorous exercise, especially cycling, within 48 hours 
• a digital rectal examination performed just before or at the same time as the blood test 
• a prostate biopsy — PSA may remain significantly raised for up to six weeks afterwards 
• urinary tract infection — PSA may remain raised for several months 
• medicines that lower PSA: finasteride (Proscar, Propecia) and dutasteride (Avodart) are prescribed for BPH and can reduce PSA levels significantly. If you take these medicines, your doctor will adjust how they interpret your result. Other medicines including aspirin, statins, diuretics, and some chemotherapy drugs (such as cyclophosphamide and methotrexate) may also affect PSA

PSA is usually considered alongside other assessments. Your doctor may arrange: 

• digital rectal examination (DRE) — a physical examination of the prostate gland 
• free PSA test — to help interpret a borderline total PSA result 
• multiparametric MRI (mpMRI) scan — an imaging test now routinely used before biopsy to identify suspicious areas in the prostate 
• prostate biopsy — a tissue sample to confirm or rule out cancer (usually guided by MRI findings) 
• Urine culture — to check for a urinary tract infection if prostatitis is suspected 
• Tumour markers — for broader context on cancer markers