What Is IBS-A?

All About Alternating or Mixed Type IBS

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Irritable bowel syndrome - alternating type (IBS-A) is a sub-type of the health disorder known as irritable bowel syndrome (IBS). When people have IBS-A, they experience all of the typical symptoms of IBS, but without a consistent bowel habit. Therefore, a person with IBS-A finds themselves dealing with both episodes of diarrhea and constipation.  The changing nature of bowel symptoms can make it difficult to find strategies that bring about symptom relief.

Functional gastrointestinal disorders like IBS are diagnosed through the use of diagnostic criteria known as the Rome III criteria. Rome III criteria use an alternative term as they refer to IBS-A as IBS-mixed (IBS-M). The Rome II criteria used the term IBS-A and regular people are most likely to identify themselves as having IBS-A. The other IBS subtypes are constipation predominant IBS (IBS-C) and diarrhea predominant IBS (IBS-D).

Symptoms of IBS-A

The Rome III criteria define IBS-M (IBS-A) as experiencing hard, lumpy stools during at least 25% of bowel movements, and experiencing loose, mushy stools during at least another 25% of bowel movements. These stool changes can occur over periods of hours or days. Other individuals find that their predominant bowel problem alternates between weeks or months of constipation and weeks or months of diarrhea.

People who have IBS-A also have all or some of the other symptoms associated with IBS:

Note: If you are experiencing chronic episodes of constipation, diarrhea, or any of the other symptoms mentioned above, it is essential that you see your doctor in order to obtain an accurate diagnosis. Many more serious health problems share some of the same symptoms as IBS and IBS-A.

Once you have the correct diagnosis, you can work with your doctor on devising a treatment plan.

Prevalence of IBS-A

There is not a lot of data that points solely to the number of people who have IBS-A. Some studies show that approximately a third of all IBS patients have this sub-type of the disorder. One report found that a majority of IBS patients do experience an alternating pattern in terms of constipation and diarrhea, but do not necessarily describe themselves as having IBS-A.

What Causes IBS-A?

Again, there is little known as to why a person who has IBS would experience symptoms related to one or the other of the three sub-types. And with IBS-A, it is quite confusing that the underlying problems would manifest themselves with the symptom of both constipation and diarrhea. Although there may not be a specific focus on IBS-A, researchers have been looking at the factors that might be behind IBS in general. These factors include:

Treatment of IBS-A

The challenge with the treatment of IBS is that you want to ensure that efforts to ease one bowel habit problem don't inadvertently result in the opposite problem. Working closely with your doctor may help. Your doctor may recommend some or all of the approaches that are typically recommended for the treatment of IBS:


Hungin, A., et. al. "Irritable bowel syndrome in the United States: prevalence, symptom patterns and impact." Alimentary Pharmacology & Therapeutics 2005 21:1365-75

Saha, L. "Irritable bowel syndrome: Pathogenesis, diagnosis, treatment, and evidence-based medicine" World Journal of Gastroenterology 2014 20:6759–6773.

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