Alternating constipation and diarrhea may indicate a digestive tract disorder like irritable bowel syndrome (IBS). Treatment can include lifestyle and diet changes.

Many things can cause diarrhea and constipation and are often an indication of issues in the digestive tract.

The two do not commonly occur together, but the alternating nature of constipation and diarrhea is a hallmark sign of irritable bowel syndrome (IBS).

Constipation is passing stool fewer than three times a week. Stools are generally hard, lumpy, or dry, which makes them difficult or painful to pass. Around 16% of American adults have symptoms of constipation.

Meanwhile, diarrhea involves passing loose, watery stools at least three times a day. About 179 million cases of diarrhea occur every year in the United States.

This article explores the possible cause of having alternating constipation and diarrhea, their other possible causes, and when to see a healthcare professional.

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Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disease characterized by abdominal pain or discomfort and bowel movement changes, including constipation, diarrhea, or both.

Healthcare professionals use the Rome IV criteria to diagnose IBS, which requires a person to have two or more of the following symptoms for at least 3 days a month in the last 3 months:

  • improvement of abdominal pain or discomfort upon passing stool
  • changes in stool frequency
  • changes in the appearance or form of stool

The Rome IV criteria classify IBS into four subgroups, depending on the predominant symptom:

  • IBS with predominant constipation (IBS-C)
  • IBS with predominant diarrhea (IBS-D)
  • IBS with mixed bowel habits (IBS-M)
  • IBS Unclassified (IBS-U)


Doctors do not know the exact cause of IBS. They believe that a number of factors may play a role in its development, including:

  • Increased intestinal sensitivity
  • altered intestinal motility
  • brain-gut interaction
  • psychosocial distress


People with IBS experience many different symptoms, so healthcare professionals tailor treatments to address these specific issues. Treatments also vary per IBS subclassification since each has different symptoms.

Although there are a wide variety of treatments for IBS, only a few target all IBS symptoms at once, and most treatments focus solely on individual symptoms.

Treatments that can help IBS symptoms include:

Many causes can contribute to a person’s constipation. These include:

  • pelvic floor disorders
  • taking certain medicines and dietary supplements
  • pregnancy
  • being older
  • ignoring the urge to pass stool
  • changes in food amount and intake
  • not drinking enough fluids
  • not eating enough fiber
  • not getting enough physical activity

Certain conditions are also more likely to become constipated, including hypothyroidism and diabetes.

The most common causes of short-term (acute) diarrhea are:

  • infections (viral, parasitic, or bacterial)
  • eating contaminated food or water
  • certain medications like antacids and antibiotics

Chronic diarrhea, or having diarrhea for 4 or more weeks, has the following causes:

IBS symptoms may be challenging to manage, and sudden worsening of symptoms, or flares, are common.

However, a person should be aware of red flags or changes inconsistent with IBS symptoms. These include:

Alternating constipation and diarrhea is a hallmark sign of IBS-M, a sub-classification of IBS. Treatment for IBS depends on its symptoms. People can find effective treatments for their IBS symptoms by working closely with a healthcare professional.

A person should also be aware of other causes of constipation and diarrhea and red flags that warrant further medical attention.