Alternating or Mixed-Type Irritable Bowel Syndrome

Irritable bowel syndrome alternating type (IBS-A) is a subtype of irritable bowel syndrome (IBS). When you have IBS-A, you experience all of the typical symptoms of IBS, but without a consistent bowel habit. You will find yourself 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.

A doctor talking with her patient
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Rome Criteria for IBS With Mixed Bowel Habits (IBS-M)

IBS is a functional gastrointestinal disorder diagnosed by applying standards known as the Rome criteria. Instead of IBS-A, the current Rome IV criteria changed to using the term "IBS with mixed bowel habits" (IBS-M). You are likely to continue to hear some people call it IBS-A. The other IBS subtypes are constipation-predominant IBS (IBS-C) and diarrhea-predominant IBS (IBS-D) and IBS-unclassified.

The Rome IV criteria changed the definitions of the subtypes of IBS from a percentage of all bowel movements to a percentage of bowel movements on symptomatic days only. This change allowed far more people who fell into the unclassified category to have their disorder fall under one of the three categories. IBS is considered to be a spectrum rather than the categories reflecting distinct disorders.

Symptoms of IBS-A

The Rome IV criteria define IBS-M (IBS-A) as experiencing hard, lumpy stools during at least 25% of bowel movements on symptomatic days, and experiencing loose, mushy stools during at least another 25% of bowel movements on symptomatic days. 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. The criteria no longer count bowel movements on days when you don't have symptoms.

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.

IBS Doctor Discussion Guide

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There is not a lot of data that points solely to the number of people who have IBS-A. Some studies show that approximately three-quarters of all IBS patients have this subtype 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. The Rome IV criteria were redefined so more patients would fall into one of the other three categories rather than the unclassified category.


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:


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.

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