Bile acid diarrhoea (bile acid malabsorption)

What is bile acid diarrhoea?

Bile is made in the liver and helps digest fats. Most bile acids are reabsorbed in the last part of the small bowel (the ileum) and recycled. When that recycling fails, or when the liver makes more bile acid than the ileum can take back, extra bile acids reach the large bowel. They draw in water and salt. The result is bile acid diarrhoea (BAD).

You may also see the older labels bile acid malabsorption or bile salt malabsorption. Guts UK uses bile acid diarrhoea. Type II is often over-production rather than true malabsorption, so BAD is the clearer name. We use BAD throughout this page.

Guts UK states that bile acid diarrhoea affects up to 1 in 100 people in the UK. Guts UK also says that about 1 in 3 people with IBS-type diarrhoea may have undiagnosed BAD. The BSG 2018 chronic-diarrhoea guideline notes that up to 30% of people with IBS-D have evidence of bile acid diarrhoea on SeHCAT testing.

Types I–III

• Type I — a problem in the ileum, where bile acids are normally taken back into the body. Causes include ileal resection and ileal inflammation (for example Crohn’s disease or after some cancer treatments).
• Type II — no structural cause is found (primary BAD). Guts UK notes this is often over-production of bile rather than true malabsorption.
• Type III — other abdominal conditions associated with BAD, including gallbladder removal, radiotherapy or chemotherapy, small bowel bacterial overgrowth, and bariatric surgery.

Common symptoms

• Watery or loose stools, often frequent
• Urgency, and sometimes incontinence
• Night-time bowel movements for some people
• Stools that can be pale, greasy, hard to flush, or green, yellow or orange
• Bloating, cramping, wind, nausea, or tiredness

Symptoms can look like diarrhoea-predominant IBS. That overlap is why people are sometimes told they “just have IBS-D”. BAD is a distinct condition with its own tests and treatments. It should not be treated as IBS-D by default.

Diagnosis and the SeHCAT tension

The usual specialist test is a SeHCAT scan (tauroselcholic [75 selenium] acid): a capsule or drink containing a labelled bile acid, then scans a week apart to see how much is retained. Guts UK notes that GPs cannot request it; you need a gastroenterology referral.

NICE HTG598 (last reviewed November 2021; diagnostics guidance later migrated to HealthTech guidance 598) says there is not enough evidence to recommend routine adoption of SeHCAT for people with unexplained chronic diarrhoea, suspected or diagnosed IBS-D or functional diarrhoea, or Crohn’s disease without ileal resection who have chronic diarrhoea. Centres already using SeHCAT may continue while collecting more data. NICE does not mandate SeHCAT, and it does not recommend it as routine NHS practice.

The BSG 2018 guideline on investigating chronic diarrhoea in adults still advises making a positive diagnosis of bile acid diarrhoea with SeHCAT or serum C4 where locally available, and says there is insufficient evidence to prefer a blind trial of treatment over a positive diagnosis.

That is the tension to hold in mind: NICE does not recommend routine SeHCAT; BSG 2018 still advises testing. Access varies by area. Some clinicians trial a binder instead. None of that makes SeHCAT "NICE-mandated".

The American Gastroenterological Association 2019 guideline also names the SeHCAT scan as the nuclear-medicine test used in Europe for bile acid diarrhoea, and notes it is not available in North America. When a specific test is hard to get, it says an empirical trial of a bile acid binder can be considered — the same "some clinicians trial a binder" already on this page, not a NICE mandate and not a shopfront for unlicensed binders. Smalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y. AGA Clinical Practice Guidelines on the Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D). Gastroenterology 2019. PMID 31302098.

Approaches people discuss

Treatment is individual and prescribed. This is not a shopfront for binders, and it is not a page for unlicensed products.

• Established Treating an underlying Type I or Type III cause when one is found, under specialist care. Sources: Guts UK; BSG 2018.
• Established Bile acid binders (bile acid sequestrants) such as colestyramine or colesevelam, prescribed and dose-adjusted by a clinician — not DIY products. Binders also bind other medicines. Standard UK counselling is to take other medicines typically 1 hour before, or 4–6 hours after, a binder. They can also affect fat-soluble vitamins. Some tablet options are used off-licence or via shared care and are not universally available. AGA 2019 discusses bile acid binders as a class; dose, licence, and shared-care stay a UK clinician's call. Sources: Guts UK; AGA 2019 PMID 31302098.
• Emerging Dietitian-supported low-fat or trigger-aware eating. Guts UK says there is not enough evidence for one specific diet. Sources: Guts UK.
• Limited Newer agents researched in other conditions (Guts UK mentions work on medicines such as liraglutide). These are not a current standard treatment for bile acid diarrhoea.

Community insights

These are patterns people report, not outcomes we can measure and not a treatment plan:

• Urgency and fear of leaving the house often dominate daily life until a name is put to the diarrhoea.
• Many describe years of an IBS-D label before anyone mentioned bile acids or SeHCAT.
• Binders can help when the dose is right, and can cause constipation or nausea when it is not — people talk about titration with their clinician, not a fixed “internet dose”.
• Fatty meals are a common self-reported trigger; that is anecdote, not a prescribed diet.