Deoxycholic Acid (DCA), % of Bile Acids

Your gut bacteria turn cholic acid into deoxycholic acid, or DCA. This test reports DCA as a percentage of the bile acids measured in a stool sample. That percentage describes the sample's composition. It depends on both the amount of DCA and the amounts of the other bile acids included in the calculation.

This is an exploratory marker. Researchers have found changes in bile acid patterns in bowel inflammation, diarrhea, and liver disease, but most studies measured stool concentrations, other ratios, or blood levels. Those findings haven't established this stool percentage as a way to diagnose disease, estimate your cancer risk, or choose treatment.

Where This Compound Comes From

Your liver makes bile acids from cholesterol and releases them into the intestine to help you absorb fat. Most are absorbed again and recycled. Bacteria modify some of the bile acids that reach the colon.

A limited group of gut bacteria can convert cholic acid into DCA. These bacterial products are called secondary bile acids. DCA and lithocholic acid commonly account for a large part of the bile acids in healthy adults' stool.

The connection with bacteria is supported by human research, though the calculation matters. In a study of 46 people, a stool ratio comparing DCA with the combined amount of DCA and cholic acid closely tracked the abundance of a bacterial group containing DCA producers. That ratio has a different denominator from this test's percentage of total measured bile acids.

What the Percentage Means

This test uses liquid chromatography–mass spectrometry, abbreviated LC-MS. The method separates compounds and identifies them through their molecular signals. The laboratory then calculates DCA's share of the bile acids included in its panel.

Your percentage can rise because DCA increases or because other measured bile acids decrease. It can fall for the opposite reasons. It therefore doesn't directly measure how quickly bacteria are converting bile acids, how many converting bacteria you have, or how much bile reaches your colon.

A stool concentration reports the amount of DCA per quantity of stool. A timed collection can measure how much leaves your body over the collection period. These are different measurements, and evidence about one cannot automatically be applied to another.

Colitis, Crohn's, and Chronic Diarrhea

Several studies have found reduced secondary bile acids in inflammatory bowel disease, but the findings depend on the disease, its activity, and the measurement used. One study compared 62 people with inflammatory bowel disease with 17 healthy controls. Among those with ulcerative colitis, diarrhea was associated with lower stool concentrations of DCA and several other secondary bile acids. The same relationship with stool consistency wasn't found in Crohn's disease.

That study used LC-MS/MS and examined both concentrations and composition. It did not establish a standalone DCA percentage for diagnosing a flare or measuring recovery. A low percentage also cannot establish that particular bacteria are missing.

The findings in diarrhea-predominant irritable bowel syndrome are mixed. In a study of 55 people with this condition and 28 controls, some primary bile acid concentrations were higher and some secondary bile acid concentrations were lower. DCA itself was somewhat lower, but the difference was not statistically significant. This percentage cannot distinguish irritable bowel syndrome from inflammatory bowel disease or other causes of diarrhea.

Liver Disease

Liver disease can change the supply of bile acids to the gut and their processing by bacteria. A cirrhosis study found lower stool secondary bile acid concentrations and lower secondary-to-primary ratios in advanced disease. It reported concentrations and ratios rather than this test's percentage. Those broader findings do not establish that this LC-MS DCA percentage measures the severity of cirrhosis.

Fatty liver studies also require care. A study of 287 people included healthy controls as well as people with biopsy-confirmed fatty liver disease. Total stool bile acid concentrations increased with more advanced liver scarring, but an adjusted analysis did not find a significant difference in stool DCA itself. A smaller study found higher total bile acids in plasma with advanced scarring without a difference in total stool bile acid concentrations.

Primary sclerosing cholangitis causes inflammation and scarring of the bile ducts. In a small study of 26 people with this condition, higher stool DCA concentrations were associated with lower blood bilirubin. The study measured concentration rather than this percentage, and the association does not show that raising DCA protects the liver.

Colon Cancer Research

The human stool evidence is mixed. A 2025 pooled analysis found modestly higher DCA concentrations in groups classified as being at higher colorectal cancer risk, including some groups with adenomas. Its separate comparison of people with colorectal cancer and controls did not find a statistically significant difference in DCA. The studies used different assays and compared existing disease or risk groups; they did not validate this LC-MS percentage as a screening test.

Some forward-looking evidence comes from blood. In a U.S. screening cohort, women in the highest quarter of serum DCA concentrations had about 2.9 times the odds of later colorectal cancer compared with those in the lowest quarter. The association wasn't seen in men. This was a blood concentration, so the estimate cannot be applied to your stool percentage.

A European study found associations with circulating glycodeoxycholic acid and taurodeoxycholic acid. These are forms of DCA joined to glycine or taurine. Unconjugated DCA was not associated with later colon cancer in that study. The distinction between these molecules, as well as between blood and stool, changes the interpretation.

Why Lower Isn't Automatically Better

The disease associations point in different directions and often concern different measurements. They don't establish an optimal stool DCA percentage or show that deliberately raising or lowering this percentage improves health. A result at either end of a laboratory's distribution needs context; its position alone doesn't establish harm or benefit.

When Results Can Be Misleading

• Bowel transit and stool consistency: the time stool spends in the colon affects bacterial bile acid processing. Diarrhea and constipation can accompany different bile acid patterns, but stool consistency does not predict this percentage reliably in every person or condition.
• Recent antibiotics or bowel preparation: these can alter gut bacteria and stool chemistry. Recovery varies, and a universal four-week waiting period has not been validated for this DCA percentage.
• Bile acid medications: ursodiol and medicines that bind bile acids can change the stool bile acid mixture. A result during treatment reflects those effects as well as your underlying biology.
• Which bile acids the laboratory includes: the denominator is the laboratory's measured total. Panels that count different compounds can produce different percentages from similar samples. Research has also identified fat-linked bile acids that methods may miss unless extraction is designed to recover them.
• LC-MS performance: other substances in stool can weaken the instrument's signal. Extraction, calibration, separation of related compounds, and the laboratory's controls affect accuracy. Using LC-MS does not make results from different panels interchangeable.
• Collection and handling: an unrepresentative portion of stool, contamination, or handling outside the kit's instructions can reduce comparability between samples.

Understanding Serial Results

Repeated measurements can document changes in stool composition, but the size of change that would indicate meaningful improvement or worsening has not been established. A change after a diet or medication change also doesn't prove that the change improved your health.