Does IBS Cause Diarrhea? Symptoms & Treatment Options

Key takeaways:

• IBS is a chronic gut disorder. IBS-D (diarrhea) is one of its four subtypes.
• IBS is linked to depression, anxiety, chronic fatigue syndrome, chronic pelvic pain, and other conditions.
• IBS symptoms can be relieved with the right treatment, but the condition is lifelong.

Irritable bowel syndrome (IBS) is a group of functional gastrointestinal disorders. It is associated with abdominal pain and abnormal defecation. Diagnosis is based on having recurrent abdominal pain with at least two of the following symptoms at least once a week for at least three months:

• Abdominal pain is related to defecation
• Change in stool frequency
• Change in stool consistency

Patients often report increased flatulence or a bloated feeling. Some people feel a sense of urgency when they need to defecate. They may not feel as if they have emptied their bowels after using the bathroom.

It’s believed that up to 75% of people with IBS have not been formally diagnosed. There is no test for IBS, but other causes of the symptoms should be ruled out. Because the IBS diarrhea subtype is more prevalent than others, it’s natural to wonder if your diarrhea may be linked to undiagnosed IBS.

Does IBS typically cause diarrhea?

IBS-D often causes loose, watery stools that are sometimes mixed with mucus. Defecation is associated with crampy abdominal pain and usually occurs in the daytime—particularly in the morning. Diarrhea can also occur in mixed and unclassified IBS subtypes.

If your stools are greasy, large in volume, bloody, or occur at night, you should undergo an evaluation to make sure there are no other causes for your symptoms.

Why IBS may cause diarrhea

IBS is linked to numerous medical conditions. A few of these include anxiety, depression, PTSD, food allergies, or a history of a severe gastrointestinal infection.

Some of the underlying causes of IBS are:

Altered gut motility

When you eat something, the muscles of the intestine get activated. This occurs both as a result of ingesting something and from the effects of cholecystokinin, a hormone released by the small intestine that causes bile to be released by the gallbladder.

When the gut motility is altered, food may pass more quickly through the gastrointestinal tract, causing diarrhea. If gut motility is slowed, constipation may occur.

Changes in the microbiome of the gut

The gut microbiome refers to the microorganisms in a healthy intestine. These include bacteria, viruses, and fungi. They aid digestion and may also boost your physical and mental health. In IBS, the balance of good bacteria that help digestion is often altered.

Good bacteria also keep harmful bacteria from taking over the gut. Those with IBS may have more harmful bacteria than a person with a healthy digestive tract. Chemicals produced by harmful bacteria can lead to gut motility changes.

Increased gut permeability

The lining of the intestine is called the mucosa. A gut mucosa that functions normally allows water and nutrients into the bloodstream. Larger molecules, toxins, and bacteria can be absorbed into the bloodstream if the gut becomes more permeable. These toxins may trigger an inflammatory immune response that results in diarrhea.

Other factors that often alter gut permeability include psychological stress, diet, and alcohol consumption. Altered gut permeability is also linked to the spread of harmful bacteria to other organ systems.

Altered gut permeability is linked to IBS, ulcerative colitis, Crohn’s disease, and other gastrointestinal disorders. It is also linked to conditions that occur outside of the digestive system, such as Alzheimer’s disease, diabetes, and asthma.

Increased sensitivity in the gut (visceral hypersensitivity)

The gut is sometimes referred to as the body’s second brain due to its large number of nerve cells. These neurons (nerve cells) are more sensitive to stimulation in people with IBS.

People with IBS often have a lower pain threshold than people without IBS. They are more likely to respond to bloating in the stomach and intestines.

Stress

IBS is considered a neurogastrointestinal disorder. The nerve cells in the gut and brain communicate by releasing chemicals known as neurotransmitters, which relay signals resulting from nerve stimulation. These signals may cause increased bowel motility, leading to diarrhea.

IBS symptoms can occur with psychological stressors such as anxiety, PTSD, and depression. Childhood stressors like trauma or abuse also predispose individuals to IBS.

Food sensitivities and allergies

Gluten sensitivity, along with other food sensitivities and allergies, has been linked to IBS. Dairy or foods that make you feel flatulent or bloated can also cause IBS. Broccoli, cabbage, and Brussels sprouts are three such foods.

Post-infectious IBS

In some cases, a person may develop IBS after a severe gastrointestinal infection. This can occur after an infection with viruses, bacteria, worms, or parasites.

Read our guides on types of diarrhea and common causes of diarrhea for more.

How to tell if IBS is causing diarrhea

No single test can diagnose IBS. However, if you meet the diagnostic criteria and have no structural problems in your gut, you most likely have IBS. Your doctor will take a careful history and perform a physical exam before making a diagnosis.

Usually, blood in stool is tested to rule out causes like inflammatory bowel disease (different from IBS), cancer, or infection. You may also have a hydrogen breath test to determine if a condition called small intestinal bacterial overgrowth is causing your diarrhea. Sometimes, your doctor may order abdominal X-rays, a CT scan, or a colonoscopy.

How to get immediate relief from diarrhea if you have IBS

IBS is a chronic disease and does not have a cure. Treatment aims to reduce or relieve your symptoms. If you are having diarrhea frequently, you may try over-the-counter treatment, or your doctor may prescribe one of the following therapies:

Antidiarrheal drugs

Antidiarrheal medications can increase the time it takes for food to transit the digestive system. Two common ones are:

• Loperamide (Imodium), an over-the-counter medication frequently used to stop or prevent diarrhea. It reduces the movement of the intestinal muscles. It also minimizes the loss of fluids and electrolytes and decreases stool volume.
• Diphenoxylate and atropine (Lomotil), a prescription antidiarrheal drug that acts through the autonomic nervous system.

Antispasmodics

Antispasmodics relax the muscles of your intestine to help relieve cramps and abdominal pain. They also reduce sweating and salivation and relax the bladder.

Common antispasmodics include:

• Hyoscyamine (Levsin, Losinamine)
• Dicyclomine (Bentyl)
• Peppermint oil

When to see a doctor about IBS and diarrhea

If you have abdominal pain and diarrhea, you may have IBS-D. It is essential to see a doctor and exclude other causes of these symptoms.

You should see a doctor if you have any of the following symptoms:

• Abdominal pain and diarrhea that persist or worsen
• Unexplained weight loss
• A family history of colorectal cancer or inflammatory bowel disease
• Black or bloody stools
• Nighttime diarrhea
• Symptoms of anemia (pallor, fatigue)

You should go to the emergency room if you have one of the following symptoms along with IBS symptoms:

• Fever
• Severe abdominal pain
• Rectal bleeding

Questions to ask your doctor about IBS and diarrhea

If you decide to see a doctor for symptoms of IBS, you may want to consider asking the following questions:

• How should I determine if specific foods trigger my symptoms?
• What if I have bouts of both diarrhea and constipation?
• Which tests might you order to find out the cause of my symptoms?
• What symptoms signal the need to go to the emergency room?

How to manage IBS long-term and prevent diarrhea

If you have IBS-D, your doctor may recommend several therapies to help manage your condition. If the treatments below do not help, there are many second-line options.

Antidepressant medications

Several antidepressant medications have pain-relieving effects for many users. They also help to relieve depression and stress, which may trigger or contribute to IBS-D.

Selective serotonin reuptake inhibitors include:

• Fluoxetine
• Fluvoxamine
• Sertraline
• Paroxetine

Tricyclic antidepressants are an older class of antidepressant medications that act on the autonomic nervous system. They can also reduce intestinal transit time. Some tricyclic antidepressants include:

• Nortriptyline
• Amitriptyline
• Imipramine
• Doxepin

Loperamide (Imodium)

Your doctor may recommend taking two mg of loperamide (Imodium) 45 minutes before meals as a preventive measure. Loperamide should be limited or not prescribed for some IBS patients.

Rifaximin (Xifaxan)

Rifaximin is an antibiotic. If you have IBS-D and your diarrhea remains frequent, your doctor may prescribe a two-week trial of Rifaximin. Rifaximin is also used to treat travelers' diarrhea and hepatic encephalopathy.

Dietary changes

Your doctor might ask you to:

• Avoid dairy products, as lactose intolerance is common in people with IBS.
• Avoid cruciferous vegetables like broccoli, cauliflower, Brussels sprouts, and cabbage, which often increase bloating and gas.
• Avoid legumes (beans), which are also known to increase bloating and gas.
• Avoid gluten. Gluten is found in pasta, grains, and flour. People with IBS often have some gluten sensitivity.
• Try a diet low in FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols).
  • These foods are carbohydrates that are hard to digest. Fermentable foods also allow bacteria to produce gas.
  • Some foods you may want to avoid include onions, garlic, high-fructose corn syrup, nuts, and seeds.
• Increase dietary fiber or take a fiber supplement. This can improve the consistency of your stool if you have diarrhea-predominant IBS.

Counseling

Several forms of therapy are often effective in the treatment of IBS. These include:

• Biofeedback
• Cognitive behavioral therapy (CBT)
• Hypnotism

Frequently asked questions: IBS and diarrhea

If you have symptoms of IBS-D, you probably have a lot of questions. Here are answers to some questions people frequently ask about this condition.

What foods can you avoid to calm an IBS flare-up with diarrhea?

Avoid dairy, gluten, and foods known to cause excessive gas. These include broccoli, cabbage, and beans.

How long do IBS flare-ups with diarrhea typically last?

Although the length of flare-ups can vary, most people have flare-ups lasting two to four days.

Final thoughts

Irritable bowel syndrome causes abdominal pain and changes in bowel movements, among other symptoms. IBS-D is the IBS subtype most closely associated with diarrhea. While IBS has no cure, there are short treatments that are often effective at relieving symptoms quickly. Long-term treatments can manage symptoms and reduce flare-ups.

General Medicine follows a strict editorial process, including using real experts to write our articles, vetted primary sources, fact-checking, a secondary medical review, and updates as necessary. This article was medically reviewed and fact checked by Dr. Lane Thaut, DO.

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