Patient information from BMJ

Irritable bowel syndrome

Last published:Nov 30, 2023

Irritable bowel syndrome (IBS) is a condition that can cause stomach pain, cramps, bloating, constipation, and diarrhoea. It affects about 12 in every 100 adults in the UK.[1]​ Women are more likely than men to get IBS. There is no cure, but lifestyle changes and treatments can help relieve your symptoms.

What is it?

IBS affectsparts of your digestive system.

Doctors aren't sure exactly what happens in your body if you have IBS. But they think the muscles that make up the wall of your bowel don't work as well as they should. Your bowel is the part of your digestive system that turns food your body doesn’t need into solid waste. The muscles in your bowel usually tighten (contract) and relax in a coordinated way to move food along your bowel.

But these contractions might be stronger and last longer than normal if you have IBS, which can cause bloating, cramping, and diarrhoea. Or they might be weaker than normal, meaning that waste stays in your bowel for longer than usual. If this happens, too much water might be absorbed from the waste, leading to constipation.

Doctors also think that IBS could be tied to problems with how the brain communicates with the bowel, with the wrong messages sometimes being sent to the nerves controlling the bowel muscles. Your brain might do this when you are under stress or feeling anxious.

That doesn't mean that IBS is all in your mind - signals from your brain cause real physical changes in your body. But it explains why your mood or emotions can affect your IBS.

We don't know why people get IBS. There is no obvious cause that doctors can test for. And people with IBS don't have any serious structural problems with their bowels. There are probably several different things that act together to cause the condition instead of one specific cause. You also may be more likely to get IBS if someone in your family has it.

What are the symptoms?

IBS affects people in different ways. But everyone with IBS gets pain and discomfort, which often goes away for a while once they have a bowel movement or pass gas. You might also: 

• Have diarrhoea or constipation, or episodes of both

• Feel bloated

• Have slippery, thick fluid in your stools (mucus)

• Feel as if your bowel isn't completely empty after a bowel movement.

The symptoms of IBS might flare up during times of stress and emotional difficulty.

People without IBS get these types of symptoms from time to time. But if you have IBS you get these symptoms much more often than most people.

Sometimes people worry that their IBS might lead to a more serious illness, like cancer. But IBS doesn't damage your bowel or cause more serious problems.

However, the symptoms of IBS can also be a sign of more serious illnesses, so it's important to get them checked out. You should also make sure you see a doctor if you:

• get blood in your stools

• lose weight for no reason, or

• feel tired all the time.

To diagnose IBS, your doctor might recommend having tests to rule out other problems. These might include blood tests, stool tests, x-rays, or a colonoscopy.

During a colonoscopy, a doctor inserts a thin, bendy tube with a small camera on its end into your anus. By moving the tube up into your bowel, the doctor can check for possible problems.

Many people with IBS try to cope with their symptoms themselves. But it can make a big difference if you talk to your doctor. Together you can find ways to improve your symptoms through changes to your diet and lifestyle, and with treatments. To learn more, see our leaflet Irritable bowel syndrome: what treatments work?

What will happen to me?

Your symptoms might improve in time, but IBS doesn't usually go away completely. You might be reassured to know that IBS doesn't damage your bowels or lead to more serious illnesses. How badly it affects you depends largely on whether it stops you doing the things you want to do. 

Learning about your IBS might help you feel more in control and manage your symptoms better. Joining a support group might help. Your doctor might be able to recommend one in your area.

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