Glycochenodeoxycholic Acid Test

If you have ongoing gut symptoms that defy a clean diagnosis, the bile acids in your stool may be telling a story that routine testing cannot hear. Stool GCDCA (glycochenodeoxycholic acid) is one piece of that story, reflecting how your liver builds bile acids and how your gut microbes process them on the way out.

This is an exploratory measurement. There is no universal cutoff that flips your result from normal to abnormal, and a single number rarely tells you what to do next. What it can do is sit alongside other bile acids and gut markers to reveal patterns that point toward inflammatory bowel disease, bile acid diarrhea, or disrupted liver-gut signaling.

What GCDCA Is and Why Your Body Makes It

GCDCA (glycochenodeoxycholic acid) is one of the main bile acids your body produces. Your liver starts with cholesterol, turns it into a bile acid called CDCA (chenodeoxycholic acid), then attaches a small amino acid called glycine to it. That glycine attachment makes the molecule better at dissolving fat and easier for your body to manage.

Once made, GCDCA travels into your gallbladder, gets dumped into your small intestine after meals, helps you absorb dietary fat, and then most of it is reabsorbed and recycled back to the liver. A small fraction passes into your stool, where this test picks it up. The amount that lands in your stool reflects three things at once: how much your liver is making, how well your gut is reabsorbing what was sent down, and how aggressively your gut microbes are chemically modifying it.

Inflammatory Bowel Disease

The clearest use case for stool GCDCA is helping distinguish two forms of inflammatory bowel disease. In a study of people with active inflammatory bowel disease, the share of GCDCA in stool separated ulcerative colitis from Crohn's disease with about 74% specificity and 63% sensitivity. In plain terms, when stool GCDCA fell above a small threshold (roughly 0.008% of total bile acids), the result correctly flagged ulcerative colitis in most cases and correctly cleared Crohn's disease in three out of four.

This matters because the two diseases look similar on the outside but require different treatment paths. A bile acid pattern that points toward one or the other adds information that endoscopy and standard inflammatory markers cannot provide on their own.

Liver Disease and Fibrosis

Most of what is known about GCDCA comes from blood-based measurements rather than stool, so the connections below come from serum studies and apply to the underlying biology rather than to your stool number specifically. Serum GCDCA rises step by step as chronic liver disease worsens, tracking severity in primary biliary cholangitis and autoimmune hepatitis. In adults with NAFLD (non-alcoholic fatty liver disease), serum GCDCA climbs alongside advancing scarring of the liver, and women with NAFLD show higher conjugated bile acids than men.

In adults who survived a childhood condition called biliary atresia, serum GCDCA stayed elevated and correlated strongly with a marker of liver fibrosis even when bilirubin looked normal. The takeaway is that bile acid backup can persist silently long after standard liver tests reassure you everything is fine.

Metabolic and Kidney Disease

In a study of 60 adults across stages of diabetic kidney disease, plasma GCDCA increased step by step as kidney function worsened, correlating with falling eGFR (a measure of kidney filtration) and rising protein in the urine. This is serum-based evidence, not stool, but it suggests bile acid handling is tied closely to kidney health in people with diabetes.

In a 2-year weight-loss trial of 515 adults, early decreases in circulating GCDCA were linked to long-term improvements in blood sugar and insulin sensitivity. So the same molecule that signals trouble in advanced disease can also signal progress when you start eating differently.

Liver Cancer Risk

In a prospective study of 600 adults followed over years, higher pre-diagnostic levels of conjugated bile acids, including GCDCA in serum, were strongly associated with higher risk of liver cancer and fatal liver disease. A separate analysis pooling 12 cohorts and 1,744 participants reached the same conclusion. These are serum studies, not stool studies, but they reinforce that conjugated bile acids are not just bystanders in liver disease.

Pre-eclampsia

In 60 pregnant women studied for pre-eclampsia, serum GCDCA alone distinguished cases from healthy pregnancies with an AUC of 0.879 (a measure of diagnostic accuracy where 1.0 is perfect and 0.5 is no better than guessing). Total bile acids and the more commonly tested glycocholic acid did not separate the two groups as cleanly. This points to GCDCA as a more sensitive signal in some pregnancy complications, though again the evidence is from serum, not stool.

Reference Ranges

Stool GCDCA does not have universally accepted clinical cutpoints. Bile acid levels in stool depend on diet, transit time, microbiome composition, and the laboratory's specific assay, and most published values come from serum, not stool. The numbers below are research-derived orientation only. Compare your results within the same lab over time.

In one fecal study of inflammatory bowel disease, a stool GCDCA share above 0.008% of total bile acids favored ulcerative colitis over Crohn's disease. For serum GCDCA, healthy fasting levels averaged 745 nanomolar in one cohort and 1,710 nanomolar in another, with the differences attributed to fasting status, biological variability, and assay platform. Asian adults tended to have higher levels than other ethnic groups.

Source: Sommersberger et al., Lipids in Health and Disease, 2023; Luo et al., PLoS ONE, 2018.

What this means for you: a single stool GCDCA value, on its own, is not a yes-or-no test for any specific disease. Its real value emerges when read alongside other bile acids in the same panel and your clinical picture.

Tracking Your Trend

For an exploratory marker like this, your own trend is more useful than any external cutoff. Bile acid levels in stool fluctuate with diet, transit time, and microbial activity, and a single reading can mislead. The signal you want is consistency: does your GCDCA share stay stable, drift up, or drop after a treatment, a diet change, or a flare?

A reasonable cadence is a baseline test, a follow-up in 3 to 6 months if you change your diet, start a probiotic, begin a bile acid sequestrant, or treat a flare, and at least annual testing if you are tracking ongoing gut or liver concerns. The trend lets you see whether what you are doing is reshaping your bile acid biology, not just the lab number.

When Results Can Be Misleading

A few things can shift stool bile acid readings in ways that do not reflect a real underlying problem:

• High biological variability: stool bile acids fluctuate substantially day to day depending on what you ate, when you ate, and how fast food moves through your gut. One result outside the expected range is not a diagnosis.
• Recent dietary fat intake: a high-fat meal in the day or two before sample collection can transiently increase bile acid output. If your goal is a stable baseline, eat your usual diet, not an unusually fatty or unusually low-fat version.
• Recent antibiotics: antibiotics reshape the gut microbes that modify bile acids. Levels may take weeks to return to your personal baseline after a course.
• Bowel preparation or diarrhea: anything that speeds transit or empties the gut alters which bile acids reach the stool collection.

Decision Pathway for Abnormal Results

If your stool GCDCA pattern looks unusual, the first step is to read it alongside the other bile acids in the same panel and your gut symptoms. If you have chronic diarrhea and a pattern suggesting bile acid malabsorption, that is a conversation with a gastroenterologist about a trial of a bile acid binder or further workup. If you have inflammatory bowel disease symptoms and a pattern that leans toward ulcerative colitis or Crohn's disease, the result adds context to endoscopy and biopsy rather than replacing them.

If your liver enzymes are also abnormal, or you have known fatty liver, an unusual bile acid pattern is worth raising with a hepatologist. The combination of standard liver tests, fibrosis scoring, and a bile acid panel paints a richer picture than any one test alone.