InstalabLoading...
InstalabLoading...
Your gut bacteria do something remarkable every day: they take bile acids your liver makes for digesting fat and chemically remodel them into entirely new molecules. These transformed compounds, called secondary bile acids, then signal back to your colon, your immune system, and your liver. The total amount in your stool is a window into how well that conversation is happening.
When that microbial workforce shrinks or shifts, secondary bile acid output changes, and research links those changes to ulcerative colitis activity, fatty liver disease severity, colon polyp risk, and cardiometabolic patterns. This is a research-grade stool marker, not a screening test your primary care doctor will order, which makes it most useful for people already paying close attention to gut and liver health.
Total secondary bile acids (sometimes shortened to total SBAs) is the sum of stool concentrations of microbially produced bile acids, mainly deoxycholic acid (DCA), lithocholic acid (LCA), ursodeoxycholic acid (UDCA), and several minor species. The number is reported in nanograms per gram of stool.
Two specific gut bacterial enzymes do most of the conversion: bile salt hydrolase, which strips off amino acid attachments from primary bile acids, and 7-alpha-dehydroxylase, which performs the chemical step that turns cholic acid into DCA and chenodeoxycholic acid into LCA. If the bacteria that carry these enzymes (mostly Ruminococcaceae, Eubacterium, Blautia, and Clostridiales species) are depleted, your stool secondary bile acid total drops.
Because the same set of microbes also produces short-chain fatty acids and influences gut barrier function, a low total tends to travel with broader signs of an unhealthy microbiome rather than appearing as an isolated finding.
The clearest signal in the human research is in ulcerative colitis (UC). In a study of 79 people with inflammatory bowel disease, fecal secondary bile acids and the ratio of secondary to primary bile acids were lower in active UC, and lower individual species (deoxycholic acid, lithocholic acid, glycodeoxycholic acid) tracked with looser stools. The same pattern did not show up in Crohn's disease, suggesting the marker behaves differently across IBD subtypes.
In children with UC and Clostridioides difficile infection, fecal secondary bile acids were significantly reduced and could distinguish disease status. The mechanism appears to be loss of the converting bacteria during inflammation, which leaves more primary bile acids in the colon and fewer protective secondary species. In observational human research on UC, restoring secondary bile acid production has been proposed as a therapeutic target.
In nonalcoholic fatty liver disease (NAFLD), fecal and circulating bile acid patterns shift in complex ways depending on stage and population. In a study of 550 people with biopsy-confirmed NAFLD, secondary bile acids were higher in mild fibrosis (stage F1), and a model using bile acid data outperformed standard fibrosis scores like FIB-4 (a routine fibrosis blood score) for identifying early scarring.
In pediatric NAFLD, the opposite pattern appeared: a study of 68 children showed reduced fecal secondary bile acids, especially lithocholic acid, alongside loss of the bacteria that make them. In cirrhosis, fecal secondary bile acids and the secondary-to-primary ratio drop substantially, reflecting profound microbiome disruption.
Higher is not always better and lower is not always worse with this marker. In early adult NAFLD, secondary bile acids can rise. In advanced cirrhosis, pediatric NAFLD, and active UC, they fall. This is not a simple good-number-bad-number test. It is a phenotype indicator that captures different things in different conditions: in early metabolic liver disease it reflects altered enterohepatic recycling, while in advanced disease it reflects collapse of the converting microbiome. That is why interpretation has to start with your clinical context, not a universal threshold.
Stool secondary bile acids have a long-studied connection to colon health. In a case-control study of 33 people, those with colorectal polyps or cancer had higher fecal total secondary bile acids and lithocholic acid than controls. In 46 Vietnamese adults undergoing colonoscopy, advanced colorectal adenomas were associated with markedly higher hyodeoxycholic acid and a lower UDCA fraction in fluid sampled from the small intestine.
Mechanistically, certain secondary bile acids (particularly DCA at high concentrations) appear to promote colon cell proliferation and inflammation, which is why too much can be a problem even though too little signals microbiome dysfunction. The relationship is U-shaped rather than linear.
In a cohort of 1,234 people with newly diagnosed type 2 diabetes, higher circulating unconjugated secondary bile acids (the sum of DCA, LCA, and UDCA) were associated with higher cardiovascular disease risk. In a separate analysis of 2,709 adults, the secondary bile acid isoursodeoxycholate correlated with after-meal blood fat levels, inflammation, and appetite signals, and changed after bariatric surgery and fiber supplementation.
These findings come from blood-based bile acid measurements rather than the stool measurement this test captures. The two are biologically connected but not identical, so circulating findings should be read as supportive context rather than direct evidence about your stool number.
There are no universally standardized clinical cutpoints for total secondary bile acids in stool. Different commercial labs use different methods (most commonly liquid chromatography mass spectrometry) and report results in nanograms per gram, with reference ranges drawn from their own healthy populations. Treat your number as a baseline against which to compare future results from the same lab, not as a pass/fail threshold.
The most clinically meaningful information often comes from the ratio of secondary to primary bile acids and from the percentage breakdown of individual species, not from the total alone. In published research on ulcerative colitis, a depressed secondary-to-primary ratio combined with reduced DCA and LCA was the most informative pattern. Most stool bile acid panels report both the absolute totals and the species-level percentages, which is why the panel as a whole tells you more than this single line.
A single stool bile acid measurement can vary substantially day to day because of diet, transit time, and microbiome fluctuations. In a study of 136 adults, six-month reproducibility was modest, meaning serial samples capture meaningful information that one sample cannot. The authors of that study explicitly recommend multiple specimens for risk estimation in research.
If you are testing because of digestive symptoms or a known gut or liver condition, get a baseline, then retest in 3 to 6 months if you are making meaningful diet, fiber, or supplement changes. If your goal is general gut health monitoring, annual testing alongside a broader stool panel is reasonable. The shape of your trend over years carries more information than any one reading.
Several common factors can move your number up or down without indicating real disease:
An out-of-range total secondary bile acid result is not a diagnosis. It is a signal to look at the rest of your stool panel (calprotectin for inflammation, pancreatic elastase for digestion, microbiome composition, primary bile acids, short-chain fatty acids) and your clinical picture. Patterns to investigate further include low secondary bile acids combined with elevated calprotectin (which suggests gut inflammation worth seeing a gastroenterologist about), and high secondary bile acids combined with personal or family history of colon polyps (which is a reason to make sure colonoscopy screening is up to date).
If your total is markedly low and you have known liver disease, a hepatologist can help interpret the finding alongside liver enzymes, fibrosis markers, and bile acid blood tests. If you do not have an obvious clinical context, the most useful next step is usually to repeat the test in 3 to 6 months alongside a fuller microbiome and digestion workup to see whether the pattern persists.
Evidence-backed interventions that affect your Total Secondary Bile Acids level
Total Secondary Bile Acids is best interpreted alongside these tests.