saudigastro.com/patients/functional-diarrhea
Category
Common
Red flags
5
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
What is it?
Functional diarrhoea is a disorder of gut-brain interaction in which a person has loose or watery stools in at least a quarter of bowel movements, without the pain or bloating that would suggest irritable bowel syndrome (IBS, a condition of belly pain with bowel changes). "Functional" means the bowel works abnormally, but tests do not show damage or disease. Before making this diagnosis, doctors check carefully for conditions that can cause diarrhoea, because several of these are treatable.
How common is it?
Chronic diarrhoea is common in the general population, and a good share of people with it turn out to have a functional cause. It affects both men and women and any adult age.
Why does it happen?
The exact cause is not known. Food may move too quickly through the bowel, the gut may be unusually sensitive, or the gut bacteria and bile acids (digestive substances made by the liver) may play a role. Infection can sometimes trigger it. Stress and anxiety often worsen symptoms. Because many other conditions cause chronic diarrhoea, including coeliac disease, inflammatory bowel disease, microscopic colitis, bile acid diarrhoea, lactose intolerance and thyroid disease, these need to be excluded.
Symptoms
- Frequent loose or watery stools, often urgent
- Urgency, the sudden need to reach a toilet
- Little or no belly pain between or before bowel movements
- Mild bloating or gurgling sounds in some people
- Symptoms often worse after meals or in stressful periods
- Usually no waking from sleep to open the bowels
Red flags — seek urgent medical care
Blood in the stool or black stools
Not typical of functional diarrhoea and needs prompt investigation. Go to emergency if the bleeding is heavy or you feel faint.
Unintentional weight loss
May reflect poor absorption or another illness. See a doctor soon.
Diarrhoea waking you at night, fever, or severe or constant belly pain
Suggests an inflammatory or infective cause. Needs medical review; go to emergency if severe.
Signs of dehydration: very dry mouth, dizziness, passing little urine
Needs fluids and medical help urgently, especially in older adults and people with kidney disease.
New diarrhoea after age 50, or a family history of bowel cancer or coeliac or bowel inflammatory disease
Raises the need for tests such as colonoscopy.
How is it diagnosed?
Diagnosis starts with a careful history and examination. Blood tests check for anaemia, inflammation, thyroid problems and coeliac disease. A stool test for inflammation (calprotectin) helps separate bowel inflammation from functional disease, and stool tests may look for infection. A colonoscopy (a camera test of the large bowel) with small tissue samples may be done, particularly if you are older or have warning signs, to look for conditions such as microscopic colitis. Tests for bile acid diarrhoea may be considered. Functional diarrhoea is diagnosed when these are normal and symptoms fit the pattern.
Outlook — what to expect
Functional diarrhoea is not dangerous and does not lead to cancer or inflammatory bowel disease. Symptoms can be long-lasting and may fluctuate, but most people find a combination of diet changes, medicines and stress management brings good control.
Treatment
Habits & Lifestyle
Daily habits can reduce how often symptoms flare.
- Keep a diary of foods, stress and bowel movements to find your triggers
- Eat regular meals and avoid very large meals
- Be active; regular gentle exercise helps the gut
- Learn stress-management techniques such as relaxation or mindfulness; talk to your doctor about gut-focused psychological therapy
- Drink enough fluid to replace losses
Diet
Diet is often the first step. Try changes one at a time and avoid restrictive diets without guidance.
- Reduce caffeine (coffee, tea, energy drinks), which speeds the bowel
- Limit sugar-free sweeteners such as sorbitol and xylitol found in sugar-free sweets and gum
- Cut back on very fatty or fried foods and large amounts of alcohol
- Soluble fibre (oats, psyllium) can firm the stool; avoid a sudden large increase in fibre
- Test for lactose or other food intolerance only with your doctor or dietitian's guidance
Medications
Medicines can help, but should be chosen with your doctor, as they are not suitable for everyone.
- Loperamide (an anti-diarrhoea medicine) can reduce frequency and urgency; your doctor advises how to use it safely
- Bile acid binders may help if bile acid diarrhoea is suspected
- Other medicines that calm the gut may be tried in persistent cases
- Do not use antibiotics or herbal laxatives on your own; review any regular medicines that can cause diarrhoea with your doctor
Procedures & Surgery
Procedures are used to look for other causes rather than to treat functional diarrhoea.
- Colonoscopy with biopsies helps exclude inflammation and microscopic colitis
- Upper endoscopy with small bowel biopsies checks for coeliac disease when blood tests suggest it
- Breath tests or other tests may be used in selected cases for bacterial overgrowth or sugar intolerance
In the Saudi context
If you fast during Ramadan, diarrhoea can lead to dehydration, so discuss with your doctor whether fasting is safe for you. Large, rich or sweet iftar meals and strong coffee or tea can trigger symptoms in some people.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Which tests have excluded other causes of my diarrhoea?
- Could I have bile acid diarrhoea, coeliac disease or microscopic colitis?
- Is it safe for me to use loperamide, and how often?
- Would a dietitian or gut-focused psychological therapy help me?
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Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide