Constant Diarrhea and Gas: 9 Causes Explained.

Our content is not intended nor recommended as a substitute for medical advice by your doctor. Use for informational purposes only.

Diarrhea is defined as using three or more loose or liquid stools per day (reference).

Diarrhea is classified into three categories:

  • Acute diarrhea: Diarrhea lasting 1-15 days (2 weeks).
  • Persistent diarrhea: diarrhea lasting 15-30 days (About four weeks).
  • Chronic diarrhea: diarrhea lasting more than 30 days.

The cause of constant diarrhea and gas depends on the duration of the symptoms. Constant diarrhea and gas for more than four weeks are commonly due to irritable bowel syndrome, food intolerances, bile acid diarrhea, and others.

Acute and persistent diarrhea (less than four weeks) is usually due to gut bugs. Viruses, bacteria, and protozoa can cause constant diarrhea and gas for shorter periods (usually a few days to a few weeks).

The causes of constant diarrhea and gas are discussed below according to the time frame.


Causes Constant diarrhea and gas for more than 30 days.
1- Irritable bowel syndrome with diarrhea.
2- Bile Acid Diarrhea.
3- Food Intolerance.
4- Celiac disease.
5- Chronic infections of the gut tract.
6- Medications.
7- Inflammatory Bowel disease.
8- SIBO.
9- Chronic Pancreatitis.
10- Others.
Causes of constant diarrhea and gas less than 30 days
1- Viral Gastroenteritis (stomach flu).
2- Other infections and food-borne illnesses.
3- Recent drug use (especially antibiotics).

1- Irritable bowel syndrome with diarrhea.


IBS is a functional disease. Functional means that the doctor couldn’t find anything wrong in the colon and stool by investigations.

It is one of the most common diseases. About 10-15% of people worldwide have IBS (reference).

IBS is a syndrome of chronic abdominal pain and stool changes (diarrhea or constipation).

Diarrhea-predominant IBS is a very common cause of constant diarrhea and gas.

IBS is an underdiagnosed condition. Only 40% of people matching the diagnostic criteria of IBS seek medical advice (reference).

This leaves 60% of IBS sufferers unaware that they have such a condition.


Symptoms suggestive of IBS include:


  • Abdominal Pain: it is often recurrent or constant (occurring at least one day per week for the past three months).
  • The Pain is related to bowel movements (either improves or worsens with bowel movements).
  • The onset of Pain is associated with either diarrhea or constipation.
  • Constant diarrhea can occur in the IBS-Diarrhea subtype.
  • Gas and bloating.
  • Mucus in the stool.
  • Certain foods and anxiety often trigger the symptoms of IBS.
  • There are no signs of inflammation or infection, such as fever, vomiting, or weight loss.

The most common diagnostic criteria for IBS are the ROME IV criteria (Summarized in the figure below) if you suspect IBS, breath this detailed article about IBS diagnosis.

Your doctor must perform a clinical evaluation and order investigations to exclude organic and similar diseases.

This is essential before he can establish the diagnosis of IBS. You cannot diagnose IBS by yourself.


2- Food Intolerance.

Food intolerance is way more common than you think. It affects about 20% of people worldwide (reference).

The symptoms are related to the ingestion of the offending food.

If you are intolerant to one of your staple foods, diarrhea, and gas can be constant.


Symptoms of food intolerance are:

  • Gas, cramps, and bloating.
  • Diarrhea (it can be constant if you are eating the offending food daily).
  • Stomach pain.
  • Nausea.
  • Anorexia (loss of appetite).
  • A feeling of a tight band around your stomach.

The most common food intolerances include:

  • Lactose intolerance:
    Present in milk, ice cream, mustard, and some types of cheese. Lactose intolerance is a widespread condition.
  • Fructose intolerance:
    Present in many fruits and honey.
  • FODMAPs intolerance:
    It affects people with IBS. FODMAPs refer to “Fermentable Oligo-, Di-, Monosaccharides, and Polyols. FODMAPs are a group of short-chain carbohydrates that cause gas and digestive disturbances.
    They are present in various foods, vegetables, fruits, and artificial sweeteners. Learn more.
  • Caffeine intolerance:
    Caffeine in coffee, tea, and chocolates is one of the most common causes of constant diarrhea and gas. Caffeine is usually abused in large amounts, raising diarrhea risk.
  • Alcohol intolerance:
    Many alcohols cause diarrhea; some are high in FODMAPs and can trigger IBS symptoms.
  • Gluten intolerance:
    It causes Celiac disease (see later) and another milder form called “Non-celiac gluten sensitivity.”
  • Amines intolerance:
    Bacteria produce amines during food storage and fermentation.
  • Salicylates intolerance:
    Salicylates are naturally occurring chemicals. They are present in various foods, including fruits, vegetables, coffee, and teas.
  • Sulfite intolerance:
    Sulfite is used as a natural preservative for foods.
  • Food allergy:
    Some foods can cause more severe allergic reactions, such as Nuts, peanuts, raw meat, seafood, mustard, rice, and some fruits and vegetables.
    Besides the intestinal symptoms, Extra-intestinal allergic symptoms can happen. Skin rashes, urticaria, swollen lips or face, and headache are among food allergy symptoms.

Learn more about food intolerance.


3- Bile Acid Diarrhea.


Bile acid diarrhea (BAD) is a common and underdiagnosed condition. BAD can cause constant diarrhea and gas.

The condition is caused by the inability of your small intestine to handle bile acids. This occurs due to excess bile acids in your stomach or diseases affecting absorption.

BAD can cause constant diarrhea and gas for months or years.


The below statistics will explain how common is BAD:

  • Approximately 25-50% of patients diagnosed with IBS-diarrhea have BAD (reference).
  • It is estimated that about 1% of the population may have BAD.
  • About 64% of patients with Functional diarrhea have BAD (reference).
  • Up to 35% of people with “microscopic colitis” condition have BAD (reference).

Symptoms of bile acid diarrhea include:

  • Constant diarrhea with sudden urges.
  • Diarrhea constantly occurs after eating fatty meals.
  • Gas and flatulence.
  • Bloating and cramps.
  • Bile acid diarrhea is differentiated from IBS diarrhea by the characteristic severe urgency that may awaken you at night.
  • The urgency can be severe enough to cause soiling accidents.

Many doctors can overlook constant diarrhea and gas due to BAD. The BAD-specific (SeHCAT) test is relatively unavailable in all health facilities. Also, milder forms are similar to IBS-D symptoms.

“BAD” responds to a bile acid binder called cholestyramine (Questran). Learn more about the condition HERE.


4- Celiac disease.


Celiac disease is an extreme form of food intolerance. The intolerance to a protein called gluten results in severe intestinal inflammation and interferes with the absorption of various nutrients.

Gluten is a protein present in:

  • Wheat-based food (such as bread).
  • Rye.
  • Barley.

Celiac disease is a relatively common condition. It affects about 1.4% of people worldwide (reference).


Symptoms suggesting celiac disease:

  • The usual age of onset is between 20-30 years of age. But it can occur in older ages up to 70 years.
  • Abdominal Pain and bloating.
  • Constant diarrhea and gas.
  • Diarrhea can also be intermittent or not present. Constipation can also occur.
  • Nausea and vomiting.
  • Weight loss.
  • Easy fatigue and iron deficiency anemia.
  • Itchy, blistery skin.
  • Osteoporosis and osteomalacia (body aches).

Celiac disease is diagnosed by a blood test or by taking a small intestine biopsy.

Call your doctor if you suspect celiac disease. Learn more.


5- SIBO (Small Intestinal Bacterial Overgrowth).



An abnormal increase in the total bacterial population in the small intestine can lead to a condition called SIBO (small intestinal bacterial overgrowth).

SIBO is usually caused by medications (antibiotic use) or some digestive tract diseases.


Symptoms of SIBO:

  • Constant gas and bloating.
  • Diarrhea.
  • Loss of appetite (anorexia).
  • A feeling of a tight band around the stomach.
  • Sometimes, it can lead to weight loss and diarrhea.

Learn more about SIBO.


6- Chronic infections of the gut tract.


The majority of gut infections (gastroenteritis) are acute and self-limiting. However, certain organisms may cause constant diarrhea (and gas).

Common causes of chronic gut infections:

  • Parasites: Cryptosporidium, Cyclospora, Entamoeba histolytica, Giardia, and Microsporidia.
  • Bacteria: Campylobacter, Aeromonas, Closteroides difficile, E. coli, Salmonella, and Shigella.
  • Viruses: Norovirus or rotavirus.
  • Unknown cause of infectious chronic diarrhea (a condition called brained diarrhea).

People with weakened immune systems (by disease or drugs) are at higher risk of chronic infectious diarrhea.


7- Medications.


Medications are often overlooked as a cause of constant diarrhea and gas. Many medications can result in digestive problems.

Review your list to exclude medications that can cause constant diarrhea and gas.


Common medications that commonly cause diarrhea and gas:


  • Metformin and gliptins (anti-diabetes medications).
  • Antibiotics: particularly penicillins, cephalosporins.
  • Laxative overuse.
  • Stomach/GERD medications: especially Proton Pump Inhibitors such as Omeprazole (Prilosec), Esomeprazole (Nexium), and Pantoprazole (Protonix).
  • Antidepressants such as Citalopram (Celexa) and Escitalopram (Lexapro).
  • Chemotherapy.
  • Non-Steroidal Anti-inflammatory drugs: such as Ibuprofen (Advil).
  • Cholcicine (Colcrys, Mitigare).
  • Some anti-hypertensive medications include Enalapril (Vasotec) and Lisinopril (Zestril, Prinivil).
  • More than 700 medications can cause diarrhea: The complete list is HERE and HERE.

8- Inflammatory Bowel disease.


Inflammatory bowel disease is mainly used to describe two conditions

  • Crohn’s disease: Unexplained inflammation and ulceration at any part of your gut (from the mouth to the anus).
  • Ulcerative colitis: Unexplained inflammation and ulceration affecting the large intestine only (the colon and the rectum).

According to the CDC, about 1.8 million U.S. adults (0.9%) had inflammatory bowel disease.


Symptoms of IBD:


  • Recurrent or constant diarrhea.
  • Gas and flatulence.
  • Stomach (abdominal) colics.
  • Blood or mucus in stool.
  • Weight loss.
  • Generalized fatigue.
  • Fever may occur.
  • Loss of appetite.

Suspect IBD if you have a prolonged history of abdominal pain, mucus, constant diarrhea, and blood in stool without obvious cause.

The main differences between Crohn’s and ulcerative colitis are summarized in the below table.



Crohn’s Disease

Ulcerative Colitis

1- Site Any part of the GI tract (from the mouth to the anus) The colon and rectum.
2- Lesions Deeper, it can involve all the layers of the GI wall. Usually superficial (only in the innermost layer)
3-Predominant symptom Crampy abdominal Pain Bloody diarrhea. (can be constant)
4- Complications Fistulas, abscess, intestinal obstruction hemorrhagic toxic megacolon.
5- Risk of colon cancer Slight increase Marked increase

Ulcerative colitis and Crohn’s disease are major diseases that require medical care and follow-up.

If you have a long history of recurrent abdominal pain, constant diarrhea with blood, and mucus in stool, consult your doctor.


9- Others (less common).


Other causes of CHRONIC are constant diarrhea and gas. These causes are less frequent than the previously explained causes.


They include:

1. Diabetes

2. Mesenteric ischemia: decreased blood supply to the gut.

3. Lymphoma

4. Colorectal cancer.

5. Chronic pancreatitis

6. Radiation enteropathy

7. Pancreatic carcinoma

8. Hyperthyroidism

9. Cystic fibrosis.

10. Rare small intestinal diseases (e.g., Whipple’s disease, tropical sprue, amyloid, intestinal lymphangiectasia)

11. Hypoparathyroidism

12. Addison’s disease

13. Hormone-secreting tumors (VIPoma, gastrinoma, carcinoid).


Bonus 1: Causes of ACUTE constant diarrhea and gas (Usually less than two weeks).


1- Viral Gastroenteritis (stomach flu).


Viral gastroenteritis (stomach flu) is the most common cause of acute infectious diarrhea (in about 60%) (reference).

The symptoms typically are:

  • Acute onset diarrhea (usually water and yellowish or bright yellow).
  • Stomach (abdominal) cramps.
  • Nausea and maybe vomiting.
  • Sometimes, gas and bloating occur.
  • Low-grade fever.
  • It usually lasts for one to 4 days. But diarrhea may become constant for a week or two.

common infections causing bright yellow watery diarrhea

Image Data Reference


2- Other infections and food-borne illnesses.


Other infections that can cause acute attacks of constant diarrhea and gas include:

  • Bacterial infections (The non-inflammatory type).
    Bacterial diarrhea usually causes severe bloody mucus diarrhea with high-grade fever (inflammatory diarrhea).
    However, milder forms of bacterial diarrhea (non-inflammatory) can cause constant diarrhea and gas.
  • Protozoal infections (especially giardiasis).
    Giardiasis is the most common type of protozoal infection (reference: CDC). It is caused by ingesting contaminated foods or drinks.
    Giardiasis can cause severe foul-smelling, yellowish, and constant diarrhea for days or weeks.
    It also causes fat malabsorption, resulting in yellowish constant diarrhea and gas.

3- Recent drug use (especially antibiotics).


Discussed before. Enlisted here because recent drug intake can cause acute constant diarrhea and gas (less than two weeks in duration). Not necessarily chronic.


Bonus 2: When to See a doctor for constant diarrhea and gas?


  • Any constant diarrhea for more than 3 or 4 days requires medical consultation.
  • A severe form of diarrhea with more than six bowel movements per 24 hours.
  • Bloody diarrhea.
  • High-grade fever.
  • Unexplained  REPEATED attacks of constant diarrhea and gas.
  • Signs of dehydration (confusion, dry mouth, extreme thirst, fainting).
  • Age extremities (babies, elderly more than 70 years).

MORE: 8 Common Causes of Mushy Stool & Gas.