Total Bile Acids

If you've had loose, urgent stools for months and the blood tests and scopes keep coming back clean, there's a fair chance the cause is bile. In a series of 936 people with chronic diarrhea that had no other explanation, about half were losing more bile acids in their stool than normal, counting either a high total or a high share of unprocessed primary forms. More than 70% of that group improved on an inexpensive bile-binding medicine, compared with 26% of people whose stool levels were normal. Studies using the stricter nuclear-scan definition put bile acid diarrhea at roughly a quarter to a third of people with chronic diarrhea-type symptoms.

Total bile acids in stool also move with fatty liver disease, with blocked bile flow, and, in older research, with heart disease. Those links come from research cohorts, and there's no agreed healthy cutoff yet, so this is an emerging marker. It's most useful when you have gut symptoms, and it makes a reasonable baseline when you don't.

What the Number Represents

Bile acids are detergent-like molecules your liver builds from cholesterol. They're stored in the gallbladder and released into the small intestine with each meal so fat can be broken down and absorbed. Normally about 95% are pulled back in at the far end of the small intestine and sent back to the liver for reuse. Only about 5 to 10% reach the colon and leave in stool.

Once in the colon, gut bacteria rework the liver's original molecules, called primary bile acids, into secondary forms such as deoxycholic and lithocholic acid. This test adds every species together into one total, reported in nanograms per gram of stool. That total reflects three things at once: how much bile your liver is making, how well your small intestine reclaims it, and whether bile is reaching your gut at all. If your report also splits primary from secondary, that split tells you what your gut bacteria did with what arrived.

Chronic Diarrhea and Bile Acid Malabsorption

When too many bile acids escape into the colon, they draw water into the bowel and speed things along, which produces watery, urgent stools. This is called bile acid diarrhea, and it's the condition stool bile acid testing was built to find. It's common in people who've had part of the lower small intestine removed, had their gallbladder taken out, or had abdominal radiation, and it often hides under a label of diarrhea-type irritable bowel syndrome.

Sources: Vijayvargiya et al. 2020 (row 1); Borup et al. 2023 (row 2); Vijayvargiya et al. 2019 (row 3).

In these studies, stool bile acid measures picked out people with heavy, fast stools better than two blood markers, C4 and FGF19, did. Whether the primary share or the total works better is still disputed. The Mayo Clinic group found a high primary share turned up more often than a high total and caught some cases the total missed, while the 251-person prospective comparison found the single-sample total did better than the primary share against the reference scan. Most of this work used a 48-hour collection on a fixed high-fat diet and reported results in different units from this test, which uses a single sample measured per gram of stool, so your number can't be laid directly against their cutoffs.

What this means for you: if you have chronic diarrhea and your result runs high, bile acid diarrhea moves up the list, and a trial of a bile-binding medicine is the usual next step. The Canadian Association of Gastroenterology guideline recommends testing for bile acid diarrhea in chronic diarrhea and treating with a bile-binding drug when testing points this way.

Fatty Liver and Cirrhosis

In a study of 53 adults, people with the inflamed form of fatty liver disease (nonalcoholic steatohepatitis) had more bile acids in their stool than healthy controls. Higher stool totals, along with more unprocessed primary forms, tracked with higher liver enzymes and worse findings on liver biopsy. The liver seems to be making more bile acids, and more of them are slipping out unconverted.

Advanced cirrhosis runs the other way. In 61 people, those with advanced disease had lower total and secondary bile acids in stool, along with fewer of the gut bacteria that convert primary forms to secondary ones. And in 54 people with fatty liver and advanced scarring, blood bile acids rose while the stool profile didn't differ, so this test isn't a way to stage liver scarring. It shows how bile is moving through your gut, which changes in different directions at different stages of liver disease.

When Bile Doesn't Reach the Gut

A low total can mean bile isn't flowing from the liver into the intestine. In 30 people with inflammatory bowel disease, those who also had primary sclerosing cholangitis, a disease that scars the bile ducts, had a smaller total stool bile acid pool than those with bowel disease alone. The same low pattern shows up in infants with blocked or underdeveloped bile ducts.

If your total comes back low along with itching, pale stools, dark urine, or yellowing skin, treat that as a reason to get liver blood work promptly and see a clinician. A low number with no symptoms and normal liver tests is much less concerning, but it's worth repeating.

Inflammatory Bowel Disease

In ulcerative colitis and Crohn's disease, the pattern that keeps showing up is more primary and fewer secondary bile acids in stool, which points to gut bacteria that have lost some of their converting ability. In ulcerative colitis, these shifts track with blood markers of inflammation and with disease severity and symptoms. Among children with Crohn's disease, those who didn't stay in remission tended to have stool dominated by primary forms.

Most of this signal sits in the composition and less in the total, so if you have inflammatory bowel disease, the primary and secondary fractions on your report will tell you more than the single total does.

Colorectal Cancer

Secondary bile acids can irritate the lining of the colon, and diet shapes how many you make. In an older comparison, people who ate meat had about twice the ratio of secondary to primary bile acids as vegetarians. A 2025 meta-analysis linked higher stool levels of some individual bile acids, such as cholic and chenodeoxycholic acid, to colorectal cancer. The summed total, which is what this test reports, wasn't significantly associated with colorectal cancer in that analysis.

The picture isn't uniform. Among 385 people with inflammatory bowel disease undergoing cancer screening, stool bile acids weren't associated with precancerous growths or cancer. In a Danish national cohort of 2,260 people diagnosed with bile acid diarrhea, colorectal cancer risk wasn't raised, though overall cancer risk was, mainly blood cancers. A separate Danish registry study found bile acid diarrhea went along with somewhat more digestive-tract cancers over six years, about 1.6% versus 1.1%, so the cancer question isn't settled either way. A stool bile acid result doesn't replace a colonoscopy or a stool blood test for cancer screening.

Heart Disease

Turning cholesterol into bile acids and passing them in stool is the main way your body gets rid of cholesterol. In a small Israeli study, people with coronary artery disease excreted fewer bile acids than people without it. Over 20 years of follow-up in 100 people, lower excretion went along with higher long-term mortality. These were older studies using 24-hour collections and an older lab method, so take them as a pointer to the biology and not something to set a target from.

Higher looks bad for diarrhea and lower looks bad for the heart, which seems contradictory until you treat this as a flow marker with no single good direction. A high total means bile is being lost faster than the gut can reclaim it, which matters if you have loose stools. A low total can mean bile isn't arriving, or that little cholesterol is leaving the body by this route. Which reading matters depends on your symptoms and your other results.

When Results Can Be Misleading

• Lab method and units: labs measure stool bile acids with different techniques and report them per wet or dry weight of stool, so numbers from different labs or studies can't be compared directly. Use the same lab every time you retest.
• What you ate recently: dietary fat drives bile release, and the standard 48-hour test fixes fat intake for that reason. A six-month controlled feeding trial showed a higher-fat, lower-carbohydrate diet shifted the stool bile acid profile, so an unusually fatty or very lean few days before collection can skew one sample.
• Rapid weight loss: in 10 women with obesity on a very low calorie diet, total stool bile acids fell as they lost weight. That drop reflects eating less, and says nothing about digestion working better or worse.
• Medicines that are bile acids or reshape gut bacteria: ursodiol, which is itself a bile acid, raised total stool bile acids in treated infants, mostly as ursodiol. Antibiotics shift the stool profile too: in a small trial, vancomycin caused large changes in primary bile acids. Test before starting or well after finishing these if you can.

Tracking Your Trend

Stool chemistry swings with diet, bowel pattern, and medications, and levels vary a lot between people. In a study of 67 healthy young adults, the spread between individuals was nearly as large as the average itself, and stool form didn't explain it. Your own baseline is the comparison that means most.

Get a baseline. If you have symptoms or start a treatment, retest in about 3 months; otherwise, retest at least yearly. Use the same lab, and keep your eating similar in the days before each collection. If you start a bile-binding medicine, expect the number to rise while symptoms settle (see what moves this marker), so judge that treatment by how you feel and by a blood test called C4, without reading the stool number on its own.

What to Do With an Out-of-Pattern Result

High total with chronic diarrhea: this is the clearest case. A blood test called C4 is the usual companion, and it shows how hard your liver is working to replace lost bile acids. Add stool calprotectin to rule out bowel inflammation and stool fat to check fat absorption. If those fit, a trial of a bile-binding medicine is the next step, which needs a prescription.

High total with no gut symptoms: repeat it after a few normal days of eating. If it stays high, check your liver enzymes and blood lipids, since stool levels run higher in inflamed fatty liver.

Low total: check a liver panel (alkaline phosphatase, GGT, bilirubin) and blood bile acids. Abnormal liver tests or any jaundice, itching, or pale stools call for a hepatologist.

Mostly primary forms, especially with known inflammatory bowel disease: add calprotectin and bring the pattern to your gastroenterologist, since it has been tied to active or poorly controlled disease.