What does the prostate do? A plain-English guide for men

What is the prostate and where is it?

The prostate is a small gland, usually about the size and shape of a walnut. Men have one, and so do trans women and some non-binary and intersex people. It sits just below the bladder and in front of the back passage (rectum). The urethra, the tube that carries urine from the bladder and out through the penis, runs straight through the middle of it.

That position explains almost everything about prostate problems. When the prostate swells or grows, it can squeeze the urethra and change how you pee. And because it sits next to the rectum, a doctor can feel its size and texture with a gloved finger during a quick rectal examination.

What does the prostate do?

The prostate’s main job is to make part of the fluid in semen. Sperm is made in the testicles, but most of the liquid that carries it comes from the prostate and the nearby seminal vesicles. Prostate fluid helps keep sperm healthy and mobile.

The prostate also makes a protein called prostate-specific antigen (PSA), which helps keep semen runny. A little PSA leaks into the blood, and that is what the PSA blood test measures. Muscles in and around the prostate also help push semen out during ejaculation and help close off the bladder at the same time.

Does the prostate get bigger with age?

Yes. The prostate grows during puberty and then usually starts growing again slowly from middle age. The NHS says this is thought to be caused by changes in hormone levels as you get older. This growth is called benign prostate enlargement, and it is very common: according to the British Association of Urological Surgeons, about half of men have an enlarged prostate by the age of 65, and about 90% by the age of 90.

A bigger prostate does not always cause symptoms, and the size of the prostate does not match how bad the symptoms are. Some men with a large prostate notice nothing, while others with only a small increase have a lot of trouble.

What are the most common prostate problems?

Three conditions account for most prostate problems. They can cause similar symptoms, which is why a GP needs to check rather than guess:

Benign prostate enlargement (often called BPH, benign prostatic hyperplasia) is the most common cause of urinary problems in older men. It is not cancer and does not raise your risk of prostate cancer, although a man can have both. Read more in our guide to enlarged prostate symptoms.

Prostatitis means the prostate is inflamed. It can be serious, so see a GP if you have symptoms. It is treated with antibiotics, and most men feel better within two weeks, although it can take several weeks for all the symptoms to settle. When symptoms last three months or longer it is called chronic prostatitis, and you may be referred to a urologist.

Prostate cancer affects about 1 in 8 men in the UK at some point in their lives. Men over 50, Black men and men with a family history of prostate cancer – or of breast or ovarian cancer, linked to inherited genes such as BRCA2 – have a higher risk.

What are the first signs of prostate problems?

The first signs are usually changes in how you pee, because the prostate presses on the urethra or irritates the bladder. Look out for:

• difficulty starting to pee, or having to strain
• a weak, slow or stop-start flow
• feeling that your bladder hasn’t emptied properly
• dribbling after you’ve finished
• needing to pee more often or more urgently
• getting up at night to pee – see our guide to frequent urination and nocturia

Early prostate cancer often causes no symptoms at all, because it usually starts in the outer part of the gland, away from the urethra. That is why a lack of symptoms is not a guarantee, and why some men choose to discuss a PSA test with their GP.

Which urinary changes are normal ageing, and which need a doctor?

Getting up once a night, or a slightly slower flow than in your twenties, is common as you get older. But the NHS advises seeing a GP if you have difficulty peeing or need to pee more often – even if it seems minor – because the same symptoms can come from an enlarged prostate, an infection, diabetes or, sometimes, prostate cancer. Many causes are easy to treat.

What is the PSA test?

The PSA test is a blood test that measures prostate-specific antigen. A raised level can be a sign of prostate cancer, but many men with a raised PSA do not have cancer: an enlarged prostate, an infection, recent ejaculation or cycling can all push it up. A normal level does not completely rule cancer out either. There is no national screening programme for most men in the UK, but you can ask your GP about a PSA test and talk through the pros and cons. If you are 50 or over and decide to go ahead, the test is free on the NHS. Our guide to PSA levels explains the numbers by age.

Can diet or lifestyle keep the prostate healthy?

No food or supplement has been shown to shrink the prostate or prevent prostate cancer. What the evidence does support is the same as for general health: keeping to a healthy weight, staying active, not smoking and eating a balanced diet with plenty of vegetables. Some simple habits, such as cutting down on caffeine and alcohol, may also help with urinary symptoms. We look at what the research actually shows in our guide to foods for prostate health.