What is IBS

IBS is a very common gastrointestinal disorder that affects 1 in 7 people. Once known as ‘spastic colon’, abdominal pain and abnormal bowel habits (constipation, diarrhea or a mixture of both) are key features of IBS.(1) Other symptoms may also be present including:

  • bloating (the sensation of an inflated balloon in the abdomen)
  • distension ( a visible increase in abdominal girth)
  • excessive gas (farts / wind)
  • urgency to defecate (poo)

What causes IBS?

We still do not know what causes IBS, although a number of factors are thought to play a role. These includes:

Gut sensitivity

People with IBS may have a more sensitive gut - this is sometimes called ‘visceral sensitivity’

Altered gut motility

The contents of the gut may move unusually quickly or slowly - this is sometimes called ‘altered gut motility’.


People with IBS may have an imbalance of ‘good’ and ‘bad’ bacteria in their gut - this is sometimes called ‘dysbiosis’.

Leaky gut

People with IBS may have a slightly inflamed or ‘leaky’ gut that is not readily detected on usual testing.


Sometimes IBS starts after a severe gut infection such as gastroenteritis - often termed 'gastro'.

Gut sensitivity - people with IBS have an overally sensitive gut wall

People with IBS may have a highly sensitive gut wall. This means they are more sensitive to normal movements of the gut, such as stretching or distension. These normal events may be uncomfortable or quite painful in people with IBS. Around 60% of people with IBS are thought to have a highly sensitive gut wall.(2)

Altered gut motility - people with IBS have disturbances in the speed at which contents move through the gut

This means that contents move through the gut at an unusually quickly or unusually slowly. Around 1 in 3 people with IBS are thought to have this problem. If movement through the gut is unusually fast, this may result in diarrhoea. Whereas, if movement through the gut is unusually slow this may result in constipation.(3)

Bacterial - people with IBS may have alterations in their gut microbiota

The gut microbiota refers to the complex community of microorganisms that live within the gut of humans. Although we still do not know whether our gut bacteria cause IBS, some research has shown differences between the microbiota of people with and without IBS.(4)

Other possible causes of IBS - infections, 'leaky gut', etc.

Other possible causes of IBS include inflammation in the intestine or possibly, a more permeable or ‘leaky’ gut wall.

Symptoms of IBS 

It is common for the symptoms of IBS to fluctuate over time - there are good times and bad times. IBS symptoms can vary greatly between individuals and they might vary over time. These include:

Abdominal Pain

Abdominal pain or discomfort might occur anywhere in the abdomen, though most commonly it is experienced in the mid or lower abdomen.

Bowel changes

This can be constipationdiarrhea or alternating between constipation and diarrhea - meaning erratic and unpredictable bowel habits.

Bloating & Distension

Abdominal bloating where the abdomen feels full and distended, and abdominal distension where the abdomen is seen to be distended.


Excessive flatulence where passage of flatus/gas/wind is greater than usual.


Fatigue may also occur because of abdominal symptoms.

Abdominal pain

Most people with IBS experience abdominal pain, and usually, this is felt in the lower abdomen.(5) The pain can be crampy or sharp, stabbing or dull and can last minutes or hours. Often, abdominal pain will be made better or worse by defection (doing a poo). It can also be linked to a change in bowel habit.


Constipation is a common problem believed to affect about half of people with IBS.(6) People who suffer constipation often experience:

  • Difficulty passing a bowel motion (straining)
  • A feeling that the bowel is not properly emptied after a bowel motion
  • Hard or lumpy stools
  • Infrequent bowel motions
  • Sensation of blockage in the anus and/or rectum
  • Use of the fingers to remove stool

When constipation is present, this can make other IBS symptoms worse, such as abdominal pain, excessive gas, bloating and/or distension.


Loose or watery bowel motions are common in IBS. If diarrhea is present, this can result in more frequent/urgent bowel movements. In severe cases, diarrhoea can result in incontinence.

Bloating and distension

Bloating and distension are common, bothersome symptoms in IBS.(7) Bloating refers to a sensation of abdominal swelling. Patients will sometimes describe this feeling as an inflated balloon in the belly. By contrast, abdominal distention refers to an actual increase in abdominal circumference (sometimes called abdominal girth).

Because abdominal bloating and distension are different symptoms, they can occur together or separately.

People who suffer bloating and/or distension often report that these symptoms:

  • Get worse over the day;
  • Get worse with meals;
  • Improve overnight.

Will I have IBS forever?

IBS is considered a chronic condition, which means it is usually present over the long-term. However, IBS symptoms often come and go over time. Symptoms may improve or disappear for a time, and then return, or new symptoms may develop. Symptoms may also change from being quite mild, to sometimes being quite severe. Some people also find that their usual bowel habit (e.g. diarrhea or constipation) changes. For example, they may suffer mostly constipation or mostly diarrhea for a while, and then develop more of a mixed bowel habit, (sometimes experiencing diarrhea and sometimes experiencing constipation).(1)

Getting a diagnosis of IBS

IBS should not be ‘self-diagnosed’. Instead, if you suspect you have IBS, see your medical doctor for a proper diagnosis. Getting a diagnosis is important to rule out other more serious conditions, such as coeliac disease, inflammatory bowel disease and endometriosis. Your doctor can run tests to rule these conditions out. Once you are diagnosed with IBS, you can choose treatments that are best targeted to your condition.

Symptoms to tell your doctor about

There are certain symptoms that are considered ‘red flags’ or ‘alarm features’ in IBS. This is because they are sometime present in more serious conditions, such as celiac disease or inflammatory bowel disease. If you experience any of the following symptoms, make sure you tell your doctor:

  • Blood in the stool
  • Anemia
  • Weight loss that is unintentional
  • Fever
  • Symptoms that are severe or getting progressively worse
  • Daily diarrhea
  • Bowel motions at night
  • Having a family history of other bowel diseases

Your doctor may want to run additional tests to rule other conditions out if you suffer any of these symptoms.

Tests for IBS

The type and number of tests needed to diagnose IBS can vary quite a lot between individuals. If your doctor identifies no symptoms that he or she is concerned about (such as blood in the stool or anemia), few (if any) tests are needed to confirm a diagnosis of IBS. However, sometimes additional tests are needed to rule out other conditions (such as celiac disease) and to confirm the diagnosis of IBS. Common tests can include:

  • Blood tests
  • Stool tests
  • Gastroscopy/colonoscopy

Unreliable tests for IBS

There are also many tests that are widely available, but not helpful in diagnosing IBS. These include:

  • Breath tests
  • IgG food intolerance tests 
  • Faecal microbiota testing 

We do not recommend the use of these tests.

IBS Treatment

There are a large number of treatments available to manage IBS symptoms. These treatments will not cure IBS, they simply help relieve the symptoms of IBS. Some of these treatments are well supported by scientific evidence, and others are not. Working with your doctor or dietitian will help you to identify a treatment that is best suited to your main symptoms and the underlying cause of these symptoms. You may need to try several different treatments before you find one that suits your lifestyle and improves your symptoms. But remember, when trying different treatments, try only one at a time. This will give you the clearest picture about which treatments are working, and which are not.

You may be advised to begin by trying non-drug therapies. These are generally better at improving a range of symptoms, whereas drug therapies tend to target specific symptoms. An advantage of non-drug therapies is that they can often be used long-term, without ongoing costs, with few risks, and sometimes, with minimal health professional input.

Below is a list of therapies sometimes used to manage symptoms of IBS:

What is the best diet for IBS?

There are many different dietary strategies that can help relieve IBS symptoms. Research at Monash University and numerous other centres around the world has shown that a low FODMAP diet improves IBS symptoms in around 3 out of 4 IBS sufferers. Because of this, a low FODMAP diet is recommended as the first treatment choice for people with IBS.


  1. El-Serag HB, Pilgrim P, Schoenfeld P. Systemic review: Natural history of irritable bowel syndrome. Aliment Pharmacol Ther. 2004;19(8):861-70.
  2. Zhou Q, Verne GN. New insights into visceral hypersensitivity--clinical implications in IBS. Nat Rev Gastroenterol Hepatol. 2011;8(6):349-55.
  3. Sadik R, Stotzer P-o, Simrén M, Abrahamsson H. Gastrointestinal transit abnormalities are frequently detected in patients with unexplained GI symptoms at a tertiary centre. Neurogastroenterology & Motility. 2008;20(3):197-205.
  4. Simrén M, Barbara G, Flint HJ, Spiegel BMR, Spiller RC, Vanner S, et al. Intestinal microbiota in functional bowel disorders: a Rome foundation report. Gut. 2013;62(1):159-76.
  5. Mearin F, Lacy BE, Chang L, Chey WD, Lembo AJ, Simren M, et al. Bowel Disorders. Gastroenterology. 2016.
  6. Hungin AP, Whorwell PJ, Tack J, Mearin F. The prevalence, patterns and impact of irritable bowel syndrome: an international survey of 40,000 subjects. Aliment Pharmacol Ther. 2003;17(5):643-50.
  7. Maxton DG, Morris JA, Whorwell PJ. Ranking of symptoms by patients with the irritable bowel syndrome. BMJ. 1989;299(6708):1138-.
  8. Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology. 2014;146(1):67-75.e5.
  9. Peters SL, Yao CK, Philpott H, Yelland GW, Muir JG, Gibson PR. Randomised clinical trial: the efficacy of gut-directed hypnotherapy is similar to that of the low FODMAP diet for the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2016;44(5):447-59.