Cholic Acid (CA), % of Bile Acids

Bile acids can contribute to chronic diarrhea, but the individual cholic acid percentage in stool is still an exploratory measurement. It describes the composition of your sample. Its usefulness for choosing treatment or improving health outcomes hasn't been established, and there are no standardized clinical cutpoints for this individual percentage.

This test reports cholic acid as a percentage of the bile acids measured in stool by LC-MS. It differs from the combined primary bile acid percentage and total bile acid excretion used in some diagnostic evaluations. Those measurements have clinical evidence that cannot be transferred directly to this result.

Where This Number Comes From

Cholic acid and chenodeoxycholic acid are the two main primary bile acids your liver makes from cholesterol. They enter the small intestine in bile and help you absorb fats. About 95% of bile acids are reabsorbed in the intestine and returned to the liver, with much of that recovery taking place near the end of the small intestine.

Bile acids that escape this recycling reach the colon. Bacteria remove the amino acids attached to them by the liver, and certain bacteria make further chemical changes. They can turn cholic acid into deoxycholic acid. These bacteria-made products are called secondary bile acids, and they usually account for most bile acids in adult stool.

Primary and unconjugated describe different properties. Primary identifies a bile acid made by the liver; unconjugated means it has no attached amino acid. Cholic acid in stool may already have been altered by bacteria removing that attachment, even though it hasn't been converted to deoxycholic acid.

Bacterial conversion helps explain stool composition, but this percentage doesn't measure conversion directly. In one human study, the proportion of deoxycholic acid within the combined deoxycholic-plus-cholic acid pool was strongly associated with a group of gut bacteria called Clostridium subcluster XIVa. That was a different ratio from cholic acid as a percentage of all measured bile acids.

Your result also depends on bile acid delivery, intestinal absorption, movement through the bowel, and the other bile acids in the sample. The percentage can rise because cholic acid increases or because other bile acids decrease. Even a high percentage can occur in a sample containing a small total amount.

Chronic Diarrhea

Excess bile acids reaching the colon can increase fluid secretion and speed bowel movement. This can cause bile acid diarrhea. Problems with absorption near the end of the small intestine and excessive bile acid production are among the causes.

In a study of 55 people with diarrhea-predominant irritable bowel syndrome and 28 healthy controls, stool cholic acid concentrations were substantially higher in the IBS group. Higher concentrations were associated with more frequent bowel movements. The study measured the amount per gram of stool, so that difference cannot be interpreted as a difference in this percentage.

A prospective diagnostic study enrolled 251 people with chronic diarrhea, with stool results available for 179. Total stool bile acid concentration distinguished bile acid diarrhea better than the combined primary bile acid percentage. Their discrimination scores were 0.89 and 0.71, respectively, on a scale where 1 represents perfect separation. The primary measurement combined cholic and chenodeoxycholic acid forms, so neither score establishes the accuracy of cholic acid percentage alone.

Ulcerative Colitis and Crohn's Disease

Studies of ulcerative colitis have found changes in stool bile acid composition, including lower secondary bile acids and a greater primary bile acid contribution in some groups. Associations with diarrhea and inflammation have varied by the bile acid measured and the study population. These findings haven't established a standalone cholic acid percentage test for disease activity.

Inflammation, altered absorption, faster transit, and changes in bacteria can all contribute to the pattern. In Crohn's disease, disease or surgery affecting the end of the small intestine can cause bile acid malabsorption. An individual stool percentage cannot distinguish these explanations or establish that inflammation is active.

Fatty Liver Disease and Cirrhosis

A study compared 199 adults with biopsy-confirmed fatty liver disease with 88 healthy controls. Stool primary bile acid concentrations were higher in those with more advanced liver scarring, and the balance between primary and secondary bile acids differed. These were concentrations and ratios in people examined at one point in time. They don't establish that your cholic acid percentage can measure scarring or predict progression.

Cirrhosis can produce a different pattern. In one study, advanced disease was associated with lower total stool bile acids and lower secondary-to-primary ratios. That study reported amounts and ratios rather than this individual percentage. It supports a connection between liver disease and altered bile acid processing, without providing an interpretation rule for this result.

Colorectal Cancer Research

A 2025 meta-analysis found higher stool cholic acid concentrations in people with colorectal cancer or conditions associated with higher cancer risk. The evidence compared people who already had these conditions with comparison groups, using varying methods. It concerned concentrations, not this percentage, and doesn't establish a screening test or a way to predict your future cancer risk.

Why Higher Isn't Automatically Worse

In a study of 67 young adults, a stool pattern with higher cholic and chenodeoxycholic acid concentrations was associated with normal stool form. This finding concerns concentrations rather than cholic acid percentage, but it shows why primary bile acids cannot be labeled harmful whenever they are more abundant.

Secondary bile acids also have different biological effects depending on the molecule and its concentration. Neither maximizing bacterial conversion nor minimizing it is an established health goal. There is no demonstrated optimal cholic acid percentage for prevention or longevity.

When Results Can Be Misleading

• Percentage versus amount: a changing total or a change in another bile acid can move the percentage even when the amount of cholic acid stays similar.
• Different panels: laboratories may include different bile acids in their total. Two percentages can therefore have different denominators, even when both laboratories use LC-MS.
• Medications: antibiotics and some other drugs can change stool bile acid profiles. Such changes do not by themselves establish a new bowel disease or a need to change treatment.
• Temporary bowel changes: an acute illness or a change in transit can affect a stool profile. A sample taken under unusual conditions may not represent your longer-term pattern.
• LC-MS limitations: incomplete extraction from stool, interference from other stool chemicals, and inadequate separation of closely related bile acids can affect quantification. Sample handling, calibration, and the laboratory's validation procedures matter.

LC-MS separates compounds and identifies them through molecular signals. It can distinguish individual bile acids that a total bile acid assay groups together. The method's analytical precision doesn't establish that a particular percentage has a proven clinical meaning.

What a Change Over Time Means

A population study found that laboratory measurements of stool bile acid concentrations were technically reproducible, while concentrations within the same person often varied substantially across six months. The study assessed concentrations, not this individual percentage. It does not establish a clinically meaningful change for this test or show that serial testing improves care.

A repeated pattern may be useful in research or as context during a defined clinical evaluation. A rising or falling percentage alone cannot show that your gut bacteria, liver health, or long-term risk have improved.