Add-On: Zonulin
The faecal zonulin test quantifies a physiological modulator of intestinal tight junctions, used in functional practice to assess intestinal barrier integrity. Elevations suggest increased paracellular permeability and are seen in coeliac disease, IBS, IBD, dysbiosis, and systemic inflammation; the test is exploratory and method-specific, not a diagnostic standard.
1
Biomarkers
Stool
Sample
7–10 business days
Turnaround
No
Fasting
What is the Zonulin test?
The faecal zonulin test quantifies a marker of intestinal tight-junction regulation and barrier permeability. It is ordered in functional and integrative practice to assess intestinal barrier integrity in patients with chronic gastrointestinal symptoms, food sensitivities, autoimmune or inflammatory conditions, and metabolic dysfunction where intestinal hyperpermeability is suspected as a contributor. The test is offered as an add-on to comprehensive stool panels, providing a functional view of the gut barrier alongside microbiome, digestive, and inflammatory markers. Zonulin does not diagnose a single disease; rather, it adds information about one mechanism — tight-junction permeability — that may underlie a range of clinical presentations. Practitioners use it to guide interventions aimed at restoring barrier function, including dietary modification, probiotic or prebiotic therapy, and removal of triggers such as gluten or dysbiotic bacteria. Because the marker and its interpretation are not yet standardised across laboratories or endorsed by mainstream gastroenterology guidelines, it is best positioned as an exploratory tool within a broader functional assessment rather than a standalone diagnostic.
What does the Zonulin test measure?
Zonulin is the best-characterised physiological modulator of intercellular tight junctions in the intestinal epithelium. It is released by enterocytes in response to certain luminal signals — including gluten and pathogenic bacteria — and binds to protease-activated receptor 2 and the epidermal growth factor receptor, triggering rearrangement of tight-junction proteins and a reversible increase in paracellular permeability. This regulated opening allows sampling of luminal antigens by the mucosal immune system but, when dysregulated or sustained, is implicated in conditions characterised by increased intestinal permeability.
Faecal zonulin is used in functional and integrative gastroenterology as a marker of intestinal tight-junction integrity and barrier function. Elevations are interpreted as evidence of increased intestinal permeability ('leaky gut'), a contested but increasingly studied mechanism in coeliac disease, inflammatory bowel disease, irritable bowel syndrome, and systemic conditions including autoimmunity and metabolic dysfunction. Because zonulin assays lack standardisation and measure a family of proteins rather than a single molecule, results should be interpreted cautiously and in the context of the clinical picture rather than as diagnostic.
Why is the Zonulin test ordered?
- Evaluation of patients with unexplained chronic gastrointestinal symptoms (bloating, cramping, irregular bowel habits) in whom functional bowel or barrier dysfunction is suspected
- Patients with diagnosed or suspected non-coeliac gluten sensitivity, where tight-junction dysregulation may contribute to symptom generation
- Assessment of intestinal barrier integrity in autoimmune conditions (coeliac disease, Hashimoto thyroiditis, rheumatoid arthritis, type 1 diabetes) where increased permeability is proposed as a pathogenic factor
- Patients with recurrent small intestinal bacterial overgrowth (SIBO) or dysbiosis, to assess whether impaired barrier function is contributing to microbial translocation or endotoxaemia
- Work-up of metabolic dysfunction, obesity, or insulin resistance in patients where intestinal permeability and endotoxin exposure are considered relevant to systemic inflammation
- Monitoring response to barrier-restoration interventions (dietary modification, probiotic therapy, removal of gluten or other triggers) in functional or integrative protocols
- Patients with inflammatory bowel disease or post-infectious irritable bowel syndrome, where barrier impairment is well documented and may guide adjunctive therapy
Sample collection and turnaround
Sample type
Stool
Fasting required
No
Collection method
At-home collection kit
Turnaround
7–10 business days
Collection notes
Patient self-collection using a stool collection kit provided by Genova; detailed instructions are included. A small sample is transferred into the provided vial with preservative. Patients should avoid NSAIDs and, ideally, antibiotics for 2–4 weeks before collection if clinically feasible, and document recent gluten intake and medication use on the requisition. Ship the specimen to Genova on the day of collection or store refrigerated if shipping the next business day; do not freeze.
Specimen requirements
Approximately 1–2 g stool transferred into the preservative vial supplied in the kit. Follow Genova's instructions for specimen handling; the preservative stabilises zonulin and other analytes for transport. Note stool consistency and any relevant exposures (gluten, NSAIDs, infection, antibiotics) on the requisition.
What can affect Zonulin results?
Gluten is a well-characterised zonulin trigger; recent ingestion can transiently raise faecal zonulin, so timing relative to dietary exposure matters for interpretation.
Pathogenic bacteria and dysbiosis stimulate zonulin release; acute infection or antibiotic-induced microbial shifts can elevate the marker independently of chronic barrier dysfunction.
NSAIDs directly increase intestinal permeability through prostaglandin inhibition and epithelial injury, which may secondarily raise zonulin; recent use should be recorded.
Watery stools may dilute the marker; very slow transit may allow degradation. Specimen quality and consistency affect quantification and should be noted on the collection record.
Most zonulin assays measure pre-haptoglobin-2 and related peptides rather than zonulin alone, and cross-reactivity differs by platform; results are method-specific and not directly comparable across laboratories.
Acid suppression can alter the gut microbiome and promote small intestinal bacterial overgrowth, indirectly affecting zonulin; current medication should be documented.
What do Zonulin results mean?
Elevated
Increased intestinal tight-junction permeability: reported in coeliac disease, inflammatory bowel disease, irritable bowel syndrome (especially post-infectious), non-coeliac gluten sensitivity, and small intestinal bacterial overgrowth. Systemic associations include autoimmune conditions, metabolic syndrome, and states of chronic low-grade inflammation. Very high values suggest active barrier disruption, often in the setting of infection, dysbiosis, or recent gluten exposure.
Normal
A normal faecal zonulin suggests that tight-junction regulation is intact at the time of sampling. Because permeability can vary with dietary triggers, infection, and other factors, a single normal result does not rule out intermittent barrier dysfunction, and serial testing or correlation with symptom patterns may add clarity.
Reduced
Low faecal zonulin is not clinically interpreted and is considered within the normal range. It does not indicate impaired barrier function or pathology.
Note: Zonulin is a functional marker, not a diagnostic test. Results are method-specific and not standardised across laboratories, so absolute values and reference ranges differ by platform. Interpretation must account for recent dietary gluten, infection, NSAID use, and the broader clinical and microbiome picture. Elevated zonulin should not be interpreted in isolation as proof of a single disease entity but as one signal of barrier dysregulation within a comprehensive functional assessment.
Frequently asked questions
Zonulin is a protein that regulates intestinal tight junctions, controlling how open or closed the gut barrier is. Measuring faecal zonulin assesses tight-junction integrity and is used to identify increased intestinal permeability, which may contribute to gastrointestinal and systemic conditions.
How to access the Zonulin test
The Zonulin reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
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Published: October 7, 2026
Last reviewed: October 7, 2026
- Fasano A. Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiol Rev. (2011)
- Sapone A, et al. Zonulin upregulation is associated with increased gut permeability in subjects with type 1 diabetes and their relatives. Diabetes. (2006)
- Barbaro MR, et al. Zonulin, regulation of tight junctions, and mucosal barrier function in health and disease. Am J Physiol Gastrointest Liver Physiol. (2021)
- Scheffler L, et al. Widely used commercial ELISA does not detect precursor of haptoglobin2, but recognizes properdin as a potential second member of the zonulin family. Front Endocrinol (Lausanne). (2018)
- Camilleri M. Leaky gut: mechanisms, measurement and clinical implications in humans. Gut. (2019)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.