Quick Facts
- Sample: Serum or plasma (frozen)
- Fasting: Yes — 12-hour overnight fast required; morning draw preferred
- Turn-around: 10–12 days. May take longer based on weather, holiday, or lab delays.
Benefits
- Identifies a treatable cause of chronic diarrhea that is frequently missed or misdiagnosed as IBS.
- A single blood draw — far less invasive than stool-based bile acid testing.
- Helps you and your doctor explore targeted treatment (bile acid sequestrants) instead of trial-and-error.
- Convenient for walk-in lab access — no specialist referral required in many direct-access settings.
- High negative predictive value (95%) helps confidently rule out bile acid diarrhea when results are normal.
- Actionable results that can shorten your diagnostic journey for persistent GI symptoms.
Who Is This Test For?
- People with chronic or frequent loose stools that haven't responded to standard IBS treatments.
- Individuals diagnosed with IBS-D who want to explore a specific underlying cause.
- Anyone experiencing diarrhea after gallbladder removal (post-cholecystectomy diarrhea).
- Patients with Crohn's disease, radiation ileitis, or ileal resection who develop chronic diarrhea.
- Health-conscious adults who want noninvasive GI insight before pursuing complex workups.
- People whose clinician suspects bile acid malabsorption as a contributing factor.
How It Works – Just 3 Steps
- Prepare — Fast for 12 hours overnight. Avoid bile acid sequestrants for 24 hours and statins for 5 days before your draw. Schedule a morning appointment when possible.
- Give your sample — A quick blood draw is all that's needed.
- Get your results — Results are typically returned in 10–12 days. Share them with your clinician to discuss next steps.
FAQ
What does this test actually measure? It measures serum 7 alpha-hydroxy-4-cholesten-3-one (7AlphaC4), an intermediate in bile acid synthesis. Elevated levels signal that your liver is overproducing bile acids — a hallmark of bile acid malabsorption.
Is fasting really necessary? Yes. 7AlphaC4 levels fluctuate throughout the day, so a fasting morning draw gives the most accurate and reproducible result.
Can this test replace stool bile acid testing? It is a strong first-line screen, but it is not a full replacement. Some patients with borderline results or mismatched symptoms may still need a confirmatory bile acids test or further GI evaluation.
What medications affect my results? Bile acid sequestrants (e.g., cholestyramine) and statins can lower 7AlphaC4 levels. High triglycerides, alcohol use, liver disease, and metformin therapy can also influence results.
How common is bile acid diarrhea? More common than most people realize — it occurs in up to 50% of functional diarrhea cases and in 33–60% of IBS-D patients.
More Details
What is the purpose of this test?
This test screens for bile acid malabsorption (BAM) — also called bile acid diarrhea (BAD). When bile acids are not properly reabsorbed in the small intestine, excess bile acids reach the colon, causing loose or watery stools. The liver compensates by producing more bile acids, which raises serum 7AlphaC4. Measuring this marker provides a noninvasive window into that process.
Who would benefit from this test?
You are a good candidate if you have:
- Chronic diarrhea or loose stools lasting more than four weeks.
- A diagnosis of IBS-D that has not fully responded to treatment.
- Diarrhea following gallbladder removal, ileal resection, or radiation therapy.
- Crohn's disease or microscopic colitis with ongoing diarrhea.
- A clinician who suspects bile acid involvement but wants a blood-based screen first.
- BAM is co-existent in approximately 35% of microscopic colitis cases and 42% of IBD cases.
When should I order this test?
Order 7AlphaC4 when your symptoms specifically suggest bile acid diarrhea — frequent, watery stools often worse after eating — rather than as a general digestive screen. It is most useful after common causes (infection, celiac disease) have been excluded and before committing to more invasive GI workups. It is not appropriate for cholestasis of pregnancy; a separate fractionated bile acids test applies in that context.
How do I interpret the results?
- 2.5–17.5 ng/mL (normal range): Bile acid diarrhea is unlikely — explore other causes of diarrhea.
- 17.6–52.4 ng/mL (moderately elevated): Suggestive of bile acid malabsorption (83% sensitive) — discuss results with your clinician and consider a therapeutic trial.
- ≥ 52.5 ng/mL (markedly elevated): Strong indicator of bile acid malabsorption (85% specific) — GI follow-up and bile acid sequestrant therapy are likely indicated.Reference interval for adults: 2.5–
63.2 ng/mL per Mayo Clinic Laboratories. A level ≥ 17.6 ng/mL carries 83% sensitivity and 53% specificity; a level ≥ 52.5 ng/mL carries 40% sensitivity and 85% specificity for bile acid diarrhea in IBS-D populations.
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
Pre-test preparation
- Fast for 12 hours before your draw — water is fine.
- Schedule a morning appointment (before 9 a.m. when possible) as levels vary by time of day.
- Stop bile acid sequestrants (e.g., cholestyramine, colesevelam) at least 24 hours before collection.
- Stop statins at least 5 days before collection.
- Inform your provider of any liver disease, high triglycerides, alcohol use, or metformin therapy, as these can affect interpretation.
How often should I get tested?
- Initial evaluation of chronic diarrhea / IBS-D: Once, as a diagnostic screen.
- Borderline result with ongoing symptoms: Repeat in 3–6 months, or after confounding factors (statins, sequestrants) are addressed.
- Monitoring response to bile acid sequestrant therapy: As directed by your clinician — typically 3–6 months after starting treatment.
- Post-ileal resection or Crohn's disease follow-up: Per gastroenterologist's guidance; at least annually if BAM was previously confirmed.
Why early detection matters
Bile acid diarrhea is frequently misidentified as IBS, leading to years of ineffective treatment. Identifying BAM early means you can move quickly from symptom management to targeted therapy with bile acid sequestrants, which have demonstrated meaningful symptom relief in confirmed cases. A 2024 real-world study across 712 patient samples confirmed the assay's clinical adoption and utility at scale. (Labcorp / AIBD Poster, 2024) Early diagnosis also avoids unnecessary colonoscopies and specialist delays.
Related tests you may consider
Bile Acids, Fractionated and Total Blood Test — Measures bile acid levels in the blood to help diagnose and monitor liver and gallbladder diseases.
Comprehensive Metabolic Panel (CMP-14) with eGFR Blood Test — Evaluates nutrient levels, liver, and kidney function.
Lipid Panel Blood Test — Measures the amount of good and bad cholesterol to assess risk of cardiovascular disease such as heart disease, heart attack and stroke.
