Bile Acid Malabsorption: Causes, Symptoms, Testing & Natural Support

Key takeaways

• Bile acid malabsorption (BAM), also called bile acid diarrhoea, is a common cause of chronic watery diarrhoea.
• More than 1 in 4 people diagnosed with IBS-D have it. It is thought to affect about 1% of adults.
• It happens when bile acids reach the colon instead of being recycled. There, they draw in water and speed up the gut.
• There are three types: damage to the end of the small intestine, no clear cause, or linked to another condition such as gallbladder removal or SIBO.
• In the UK, it is diagnosed with a SeHCAT scan or a C4 blood test, usually through a gastroenterologist.
• The main treatment is a bile acid binder prescribed by your doctor. A lower-fat diet can help too.
• A stool microbiome test cannot diagnose BAM, but it can add context about gut bacteria.

What is bile acid malabsorption?

Bile acid malabsorption (BAM) is when bile acids are not properly recycled by the small intestine. Instead, they spill into the colon. There, they pull in water and speed up the gut, causing chronic watery diarrhoea. It is also called bile acid diarrhoea (BAD) or bile salt malabsorption [1].

Bile acids are made in your liver from cholesterol. They are stored in your gallbladder and released after you eat to help you digest fat.

Normally, your body recycles almost all of them. Less than 5% escape being reabsorbed at the end of the small intestine, called the terminal ileum [2]. The rest travel back to the liver to be used again.

In BAM, too many bile acids reach the colon. This can happen because the ileum can’t reabsorb them, or because the liver makes too many [1]. Researchers increasingly use the name “bile acid diarrhoea” because true malabsorption is not always the cause.

How common is bile acid malabsorption?

More than 1 in 4 people diagnosed with IBS-D have bile acid malabsorption. A 2015 meta-analysis of 908 patients found a pooled rate of 28% [3]. Across the general population, it is thought to affect about 1% of people [5].

An earlier review of 1,223 patients with IBS-D found these rates by severity [4]:

Severity (SeHCAT result)	Share of IBS-D patients
Severe (under 5%)	10%
Moderate (under 10%)	32%
Mild (under 15%)	26%

The studies in each row differ, so these figures don’t add up to one total. Even so, BAM is often missed, partly because many doctors don’t think to test for it [1].

What are the symptoms of bile acid malabsorption?

The main symptom is chronic, watery diarrhoea that is often urgent. Many people also have tummy discomfort and bloating [6]. People with severe BAM may also have pale, greasy stools (steatorrhoea) [7].

Common symptoms include:

• Loose or watery stools, often several times a day
• A sudden, urgent need to open your bowels
• Diarrhoea after meals, especially fatty meals
• Bloating, wind and tummy cramps
• Pale, oily or hard-to-flush stools (in more severe cases)
• Leaking or accidents (faecal incontinence)

The timing of symptoms can be a clue. If you’ve had surgery to remove part of the ileum (the last section of the small intestine), you may notice diarrhoea comes on mainly after meals. This is a typical pattern when BAM is caused by this kind of surgery [8].

Bile acid malabsorption vs IBS-D

BAM and IBS-D can feel almost the same. In one study, doctors could not tell them apart from symptoms alone. Only the SeHCAT test separated them [9].

	Bile acid malabsorption	IBS-D
What causes it	Too many bile acids reaching the colon	No single cause; gut–brain, sensitivity and motility changes
Main symptom	Watery, urgent diarrhoea	Tummy pain linked to bowel movements, with loose stools
Fatty food	Often a clear trigger	May or may not be a trigger
How it’s confirmed	SeHCAT scan or C4 blood test	Symptom criteria, after other causes are ruled out
Response to bile acid binders	Often good	Usually little effect, unless BAM is present

If you have an IBS-D diagnosis and treatment hasn’t helped, ask your GP whether BAM has been considered.

What causes bile acid malabsorption?

There are three types of BAM. Type 1 is caused by damage to, or removal of, the terminal ileum. Type 2 has no obvious cause. Type 3 happens alongside other conditions, such as gallbladder removal, coeliac disease or SIBO [1] [6].

Type	What’s going on	Examples
Type 1	The terminal ileum is damaged or missing, so it can’t reabsorb bile acids	Crohn’s disease of the ileum, surgery to remove the ileum, radiotherapy damage
Type 2 (primary or idiopathic)	No damage. The liver makes too many bile acids	Often diagnosed as IBS-D
Type 3	Another condition disturbs how bile acids are handled	Gallbladder removal, SIBO, coeliac disease, chronic pancreatitis

Why Type 2 happens

Type 2 is the most common type in people labelled with IBS-D. It seems to be a signalling problem, not an absorption problem [10].

When bile acids are reabsorbed, the ileum releases a hormone called FGF19. FGF19 tells the liver to slow down bile acid production. People with Type 2 BAM have low FGF19, so the liver keeps making bile acids. This overwhelms the gut’s ability to recycle them [10] [11].

Low FGF19 has also been found in people with diarrhoea after gallbladder removal [10].

Is bile acid malabsorption linked to SIBO?

Yes. Small intestinal bacterial overgrowth (SIBO) is a recognised cause of Type 3 BAM [1]. If you have both, treating only one may not fully settle your symptoms.

In SIBO, bacteria in the small intestine break down (deconjugate) bile acids too early. This lowers the amount of working bile acids available to digest fat, which can lead to fat malabsorption [12].

The link may also run the other way. Bile acids help keep bacteria in check, and lower bile acid levels in the gut are linked with bacterial overgrowth [13]. Whether this makes SIBO more likely in people with BAM has not been directly tested.

If your symptoms include bloating, wind or diarrhoea, a breath test can check for SIBO. Healthpath’s SIBO Test tests for both hydrogen and methane-producing overgrowth. Please note it does not test for BAM.

How is bile acid malabsorption diagnosed in the UK?

In the UK, BAM is diagnosed with a SeHCAT scan or a C4 blood test, depending on what your local hospital offers. British Society of Gastroenterology (BSG) guidelines recommend making a positive diagnosis with one of these tests, rather than just trying treatment [8]. A stool test cannot diagnose BAM.

What your GP checks first

Before testing for BAM, your GP will usually rule out other causes. BSG guidelines recommend blood tests (for example, for anaemia and coeliac disease) and a stool test for gut inflammation [8]. If BAM is suspected, you will usually be referred to a gastroenterologist.

SeHCAT scan

The SeHCAT scan is the main UK test. You swallow a capsule containing a man-made bile acid with a tiny amount of a radioactive marker. A scanner measures how much is in your body soon after, then again 7 days later. NICE has published guidance on its use [14].

SeHCAT 7-day retention	What it means	Response to colestyramine
Over 15%	Normal	—
10–15%	Mild BAM	70%
5–10%	Moderate BAM	80%
Under 5%	Severe BAM	96%

Thresholds from [15]; response rates pooled from 15 studies [4].

SeHCAT is often only available in specialist centres [15], and it is not available in many countries [1].

C4 blood test

C4 (7α-hydroxy-4-cholesten-3-one) is a substance made when the liver produces bile acids. A high fasting level suggests the liver is making too many. It is the main alternative to SeHCAT in the BSG guidelines [8].

FGF19 blood test

Fasting FGF19 is mainly used in research. In one study of 101 people with IBS-D, C4 and FGF19 had specificities of 83% and 78%. C4 was the more reliable of the two [5].

Trial of treatment

Some doctors try a bile acid binder and see if symptoms improve. BSG guidelines say there isn’t enough evidence to recommend this instead of a proper test though [8].

Where does a gut microbiome test fit?

A stool microbiome test cannot diagnose BAM. But BAM is linked to changes in gut bacteria. One study found lower bacterial diversity in people with BAM than in people with IBS-D. It’s not yet clear whether this is a cause or a result of BAM [2].

Healthpath’s Ultimate Gut Test looks at the make-up and diversity of your gut bacteria. It can add context alongside medical testing, not replace it. If SIBO hasn’t been tested for, then SIBO testing would be a more worthwhile investigation considering it’s potential to cause BAM.

How is bile acid malabsorption treated?

The main treatment is a bile acid binder (sequestrant), prescribed by your doctor. These medicines bind bile acids in the gut so they can’t irritate the colon. A lower-fat diet and treating any underlying cause, such as SIBO, can also help.

Bile acid binders

Medicine	UK brand	Form	Notes
Colestyramine	Questran	Powder mixed with water	Usually tried first, but many people find the taste and texture hard [15]
Colesevelam	Cholestagel	Tablets	Often easier to take. Use for BAM is off-label [16]
Colestipol	Colestid	Granules	Used less often in the UK

These medicines work well for many people. In one review, 70–96% of people responded to colestyramine, with the best results in severe BAM [4]. A 2023 placebo-controlled trial found colesevelam was better than placebo at bringing BAM into remission [17].

Things to know before you start:

• Off-label use. Both main binders are used off-label for BAM. This is common and your doctor will explain it [18].
• Vitamins. Binders can reduce how well you absorb vitamins A, D, E and K [18]. You may want to consider checking your levels.
• Other medicines. Binders can affect how other medicines are absorbed [16]. Ask your pharmacist how to space them.

Treating the underlying cause

For Type 3 BAM, treating the linked condition can improve the diarrhoea [18]. This might mean managing Crohn’s disease, coeliac disease or SIBO.

Newer treatments

Researchers are studying medicines that act on the FXR receptor, which helps control bile acid production. These are not yet standard treatment [6].

Can diet help bile acid malabsorption?

Yes. Eating less fat can ease symptoms in all types of BAM, and in mild cases it may be enough on its own [18]. Fat is the main trigger for bile release, so less fat means fewer bile acids reaching the colon.

In one UK study, people with BAM followed a dietitian-led diet with about 20% of energy from fat. Their gut symptoms improved in a clinically important way [19].

Low-fat swaps

One NHS hospital leaflet suggests aiming for less than 40g of fat a day [18]:

Instead of	Try
Frying	Grilling, steaming, boiling or dry roasting
Fatty meat with skin	Lean meat with skin and fat removed
Full-fat milk, cheese and yoghurt	Semi-skimmed or lower-fat versions
Generous butter, spreads and oils	About 3 teaspoons (15ml) a day in total

Ask your GP for a referral to a dietitian. They can help you lower fat without missing out on nutrients.

What about fibre?

Soluble fibre, such as oats and psyllium, is gentle on the gut and may help firm up stools. Some types may also bind bile acids, though good trials in BAM are lacking. Rougher, insoluble fibre (bran, skins, seeds) may worsen diarrhoea during flares.

A note on low-FODMAP diets

Many people with BAM have first been advised to try a low-FODMAP diet for IBS. This may ease some symptoms but doesn’t address bile acids. It is also meant to be short-term. Cutting fermentable fibre for a long time can reduce the variety of foods that feed your gut bacteria. If you try it, do so with a practitioner and reintroduce foods afterwards.

Do probiotics or supplements help bile acid malabsorption?

There is no good evidence yet that probiotics or supplements treat BAM. They don’t replace a proper diagnosis or a bile acid binder.

BAM is linked to changes in gut bacteria, including lower diversity. Some of the bacteria that change bile acids are less common in people with BAM [2]. This makes the microbiome an interesting area for research. But no trials have yet shown that a specific probiotic improves BAM.

Some supplements marketed for “bile support”, such as bitters, aim to increase bile flow. In BAM the problem is too much bile acid reaching the colon, so these are not a logical choice. Some forms of magnesium can also loosen stools. Check with your doctor or a registered practitioner before trying any supplement.

In practice, supporting a varied gut microbiome through a mix of plant foods is a sensible long-term goal, once symptoms are under control. A practitioner can help you reintroduce fibre gradually.

Can bile acid malabsorption go away?

It depends on the type. Type 3 BAM may improve if the linked condition is treated [18]. Types 1 and 2 are usually long-term, but symptoms can often be well managed with medicine and diet.

Living well with BAM often comes down to a few habits:

• Take your binder as prescribed, and space it from other medicines
• Keep fat intake steady rather than having very rich meals
• Note which meals trigger symptoms so you can plan around them
• Have regular reviews with your doctor, including vitamin checks if you take a binder long-term

The UK charity Bile Acid Diarrhoea UK offers patient support and information.

When should you see a GP?

See your GP if you have diarrhoea or looser stools that last 3 weeks or more. Long-term diarrhoea has many possible causes, and some need to be ruled out first [20].

See a GP if you have any of these for 3 weeks or more [20]:

• A change in your bowel habit that isn’t normal for you
• Blood in your poo or bleeding from your bottom
• Tummy pain, a lump in your tummy, or bloating
• Losing weight without trying
• Feeling very tired or short of breath

Ask for an urgent GP appointment or call NHS 111 if your poo is black or dark red, or you have bloody diarrhoea [20].

Don’t stop or change any prescribed medicine without talking to your doctor.

Frequently asked questions

What is bile acid malabsorption?

Bile acid malabsorption (BAM) is when bile acids aren’t recycled properly by the small intestine. They pass into the colon, where they cause watery diarrhoea and urgency. It is also called bile acid diarrhoea or bile salt malabsorption.

What are the symptoms of bile acid malabsorption?

The main symptom is chronic, watery, urgent diarrhoea, often after meals. Others include bloating, tummy cramps and, in severe cases, pale or greasy stools.

How common is bile acid malabsorption in people with IBS?

More than 1 in 4 people diagnosed with IBS-D have BAM. A 2015 meta-analysis found a pooled rate of 28%.

How is bile acid malabsorption diagnosed in the UK?

It is diagnosed with a SeHCAT scan or a C4 blood test, usually through a gastroenterologist. Your GP will first rule out other causes with blood and stool tests.

What does a SeHCAT result mean?

Retention above 15% at 7 days is normal. 10–15% suggests mild BAM, 5–10% moderate and under 5% severe.

Can you get bile acid malabsorption after gallbladder removal?

Yes. Gallbladder removal is a recognised cause of Type 3 BAM.

How is bile acid malabsorption treated?

Doctors usually prescribe a bile acid binder, such as colestyramine or colesevelam. A lower-fat diet and treating any underlying cause can also help.

What foods should I avoid with bile acid malabsorption?

High-fat foods are the main trigger, such as fried food, fatty meat and full-fat dairy. A dietitian can help you lower fat without missing out on nutrients.

Can a stool test diagnose bile acid malabsorption?

No. A gut microbiome test can’t diagnose BAM. It can show the make-up of your gut bacteria, which can add context alongside medical tests.

Is bile acid malabsorption linked to SIBO?

Yes. SIBO is a recognised cause of Type 3 BAM. Bacteria in the small intestine can break down bile acids too early.

When should I see a GP about diarrhoea?

See a GP if your bowel habits have changed for 3 weeks or more. Get urgent help if you have black or dark red poo, or bloody diarrhoea.

Scientific references

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2. Sagar NM, Duboc H, Kay GL, et al. The pathophysiology of bile acid diarrhoea: differences in the colonic microbiome, metabolome and bile acids. Sci Rep. 2020;10:20436.
3. Slattery SA, Niaz O, Aziz Q, Ford AC, Farmer AD. Systematic review with meta-analysis: the prevalence of bile acid malabsorption in the irritable bowel syndrome with diarrhoea. Aliment Pharmacol Ther. 2015;42(1):3–11.
4. Wedlake L, A’Hern R, Russell D, Thomas K, Walters JRF, Andreyev HJN. Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome. Aliment Pharmacol Ther. 2009;30(7):707–717.
5. Vijayvargiya P, Camilleri M, Carlson P, et al. Performance characteristics of serum C4 and FGF19 measurements to exclude the diagnosis of bile acid diarrhoea in IBS-diarrhoea and functional diarrhoea. Aliment Pharmacol Ther. 2017;46(6):581–588.
6. Camilleri M, Vijayvargiya P. The role of bile acids in chronic diarrhea. Am J Gastroenterol. 2020;115(10):1596–1603.
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8. Arasaradnam RP, Brown S, Forbes A, et al. Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition. Gut. 2018;67(8):1380–1399.
9. Williams AJ, Merrick MV, Eastwood MA. Idiopathic bile acid malabsorption: a review of clinical presentation, diagnosis, and response to treatment. Gut. 1991;32(9):1004–1006.
10. Walters JRF, Tasleem AM, Omer OS, et al. A new mechanism for bile acid diarrhea: defective feedback inhibition of bile acid biosynthesis. Clin Gastroenterol Hepatol. 2009;7(11):1189–1194.
11. Hofmann AF, Mangelsdorf DJ, Kliewer SA. Chronic diarrhea due to excessive bile acid synthesis and not defective ileal transport: a new syndrome of defective fibroblast growth factor 19 release. Clin Gastroenterol Hepatol. 2009;7(11):1151–1154.
12. Murphy GM. Depressing acid, deconjugating bile. Gut. 1998;42(2):154.
13. Ridlon JM, Kang DJ, Hylemon PB, Bajaj JS. Bile acids and the gut microbiome. Curr Opin Gastroenterol. 2014;30(3):332–338.
14. National Institute for Health and Care Excellence. SeHCAT (tauroselcholic [75 selenium] acid) for diagnosing bile acid diarrhoea (HTG598, formerly DG44). 2021.
15. Kumar A, Galbraith N, Al-Hassi HO, et al. The impact of treatment with bile acid sequestrants on quality of life in patients with bile acid diarrhoea. BMC Gastroenterol. 2022;22:325.
16. National Institute for Health and Care Excellence. Bile acid malabsorption: colesevelam (ESUOM22). 2013.
17. Borup C, Vinter-Jensen L, Jørgensen SPG, et al. Efficacy and safety of colesevelam for the treatment of bile acid diarrhoea: a double-blind, randomised, placebo-controlled, phase 4 clinical trial. Lancet Gastroenterol Hepatol. 2023;8(4):321–331.
18. University Hospitals Sussex NHS Foundation Trust. Bile salt diarrhoea: patient information. 2026.
19. Watson L, Lalji A, Bodla S, Muls A, Andreyev HJN, Shaw C. Management of bile acid malabsorption using low-fat dietary interventions: a useful strategy applicable to some patients with diarrhoea-predominant irritable bowel syndrome? Clin Med (Lond). 2015;15(6):536–540.
20. NHS. Symptoms of bowel cancer.

Disclaimer

This article is for general information only. It is not intended to diagnose, treat, cure or prevent any disease. Always speak to your GP or a qualified healthcare professional about your symptoms or before making changes to your medicines or diet.