Mixed-Type Irritable Bowel Syndrome (IBS-M)

Irritable bowel syndrome mixed type (IBS-M) is a subtype of irritable bowel syndrome (IBS). When you have IBS-M, 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 IV Criteria for IBS With Mixed Bowel Habits (IBS-M)

IBS is a functional gastrointestinal disorder diagnosed by applying standards known as the Rome criteria. The current version, Rome IV ("Rome 4") renames what was previously called "IBS with alternating bowel habits" (IBS-A) to "IBS with mixed bowel habits" (IBS-M). You are likely to continue to hear some people refer to it as IBS-A.

The other IBS subtypes are constipation-predominant IBS (IBS-C) and diarrhea-predominant IBS (IBS-D) and IBS-unclassified (IBS-U).

The diagnostic criteria for IBS changed in Rome IV in four main ways::

  1. The defining symptom of IBS was changed from “abdominal discomfort or pain” to just “abdominal pain."
  2. The minimum abdominal pain frequency was increased from two to three days a month to once a week.
  3. Rome IV diagnosis only requires association of pain with defecation or changes in stools.
  4. The subtypes are based only on days in which abnormal stools occur.

This change allowed far more people who fell into the unclassified category (IBS-U) to have their disorder fall under one of the three classifications, but it also cut the rate of IBS diagnoses in half.

In addition to changes above, Rome IV recommends that symptoms be present for at least the last three months, with original onset over six months before a diagnosis of IBS.

With the Rome IV criteria, many more people who used to be diagnosed with IBS are now diagnosed with functional diarrhea or functional constipation.

Symptoms of IBS-M

The Rome IV criteria define IBS-M as experiencing hard, lumpy stools (a Type 1 or Type 2 on the Bristol Stool Form Scale) during at least 25% of bowel movements on symptomatic days, and experiencing loose, mushy stools (a Type 6 or 7 on the Bristol Scale ) 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.

People who have IBS-M can have all or some of the other symptoms associated with IBS:

  • Abdominal pain
  • Changes in bowel frequency
  • Changes in bowel movement texture
  • Gas and bloating
  • A feeling of incomplete evacuation
  • Mucus in the stool

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. Some serious health problems share some of the same symptoms as IBS. Once you have the correct diagnosis, you can work with your doctor on devising a treatment plan.

IBS Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Man

Prevalence of IBS-M

There isn't much data on how many people have IBS-M specifically. The American College of Gastroenterology points out that about one half of people with IBS can change subtypes within the year, so regular reassessment of your IBS subtype is recommended.

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-M.

Causes of IBS-M

With IBS-M, it can be difficult to understand how a person can have both constipation and diarrhea. The American College of Gastroenterology acknowledges that more research is needed on IBS-M, and that it can be challenging to manage.

Researchers have been looking at the factors that might be behind IBS in general. These factors include:

A Word From Verywell

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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