{ "id": "ep5a8b3gzc", "slug": "breath-test", "title": "Breath test", "updated": "2026-10-25", "topic_path": [ { "id": "life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/topics/life" }, { "id": "life.health", "label": "Human health and medicine", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health" }, { "id": "life.health.clinical", "label": "Clinical assessment and procedures", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.clinical" }, { "id": "life.health.clinical.clinical-diagnostics", "label": "Diagnosis and clinical assessment", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.clinical.clinical-diagnostics" }, { "id": "life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics", "label": "Laboratory and in-vitro diagnostics", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics" }, { "id": "life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics.genetic-and-genomic-testing", "label": "Genetic and genomic testing", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics.genetic-and-genomic-testing" } ], "geo": [ { "id": "geo.nongeo.t1946.life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics.genetic-and-genomic-testing", "label": "Non-geographic · 1946 to 2000: Genetic and genomic testing", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics.genetic-and-genomic-testing", "path": [ { "id": "geo.nongeo", "label": "Non-geographic", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo" }, { "id": "geo.nongeo.t1946", "label": "Non-geographic · 1946 to 2000", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946" }, { "id": "geo.nongeo.t1946.life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life" }, { "id": "geo.nongeo.t1946.life.health", "label": "Human health and medicine", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health" }, { "id": "geo.nongeo.t1946.life.health.clinical", "label": "Clinical assessment and procedures", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical" }, { "id": "geo.nongeo.t1946.life.health.clinical.clinical-diagnostics", "label": "Diagnosis and clinical assessment", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical.clinical-diagnostics" }, { "id": "geo.nongeo.t1946.life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics", "label": "Laboratory and in-vitro diagnostics", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics" }, { "id": "geo.nongeo.t1946.life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics.genetic-and-genomic-testing", "label": "Genetic and genomic testing", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t1946.life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics.genetic-and-genomic-testing" } ] } ], "excerpt": "A breath test measures gases in exhaled breath to detect disease, chiefly the urea breath test for H. pylori and hydrogen tests for malabsorption and SIBO.", "snippet": "A breath test measures gases in exhaled breath to detect disease, chiefly the urea breath test for H. pylori and hydrogen tests for malabsorption and SIBO.", "node": "life.health.clinical.clinical-diagnostics.laboratory-and-in-vitro-diagnostics.genetic-and-genomic-testing", "markdown": "# Breath test\n\nA breath test is a diagnostic method that measures gases or volatile compounds in exhaled breath to detect disease. Its established clinical uses are the [urea breath test](https://www.edgepedia.org/urea-breath-test) (UBT) for [Helicobacter pylori](https://www.edgepedia.org/helicobacter-pylori) infection and hydrogen/methane breath tests for carbohydrate malabsorption (lactose, fructose) and small intestinal bacterial overgrowth (SIBO).[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/) A broader research field, breath analysis, measures the volatile organic compounds (VOCs) that breath carries for conditions including asthma, liver and renal disease, COPD, and lung cancer.[3](https://www.annualreviews.org/content/journals/10.1146/annurev-anchem-071213-020043) • [4](https://www.mdpi.com/2304-6732/12/9/848)\n\n| Key fact | Detail |\n|---|---|\n| UBT principle | H. pylori urease hydrolyzes labeled urea; labeled CO₂ is exhaled and quantified [1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) |\n| UBT accuracy | Sensitivities above 95% and specificities above 93% in typical use; pooled estimates vary between meta-analyses [1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) • [5](https://www.mdpi.com/2075-4418/12/10/2428) |\n| UBT preparation | Antibiotics and bismuth stopped 4 weeks, proton pump inhibitors (PPIs) 2 weeks before testing [1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) |\n| Lactose breath test | 25 g lactose, samples at least every 15 min over at least 3 h; a rise above 10–20 ppm in at least two samples indicates malabsorption [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/) |\n| SIBO cutoffs | A 12 ppm hydrogen rise (2026 ANMA) diverges from the ≥20 ppm North American criterion [6](https://www.jnmjournal.org/journal/view.html?doi=10.5056%2Fjnm25185) • [7](https://link.springer.com/article/10.1007/s10620-022-07487-8) |\n| Methane | Methane ≥10 ppm at baseline or any point is positive for methanogenesis [8](https://www.bsg.org.uk/getattachment/d61ac8d5-a1f0-4a73-ad2e-ebdfde4a1a2c/AGIP-Best-Practice-Statement-for-HMBT_24-01-19.pdf?lang=en-US) |\n| Breath composition | Exhaled breath contains more than 3500 VOCs [9](https://iopscience.iop.org/article/10.1149/1945-7111/ab67a6) |\n\n## How it works\n\n**Urea breath test.** UBT exploits urease, an enzyme H. pylori produces in abundance, to hydrolyze ingested isotope-labeled urea into ammonia and labeled carbon dioxide.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) The labeled CO₂ enters the bloodstream and is exhaled by the lungs, so its detection shows urease activity in the stomach and, with it, H. pylori.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) • [5](https://www.mdpi.com/2075-4418/12/10/2428)\n\n**Hydrogen and methane tests.** Pulmonary hydrogen (H₂) excretion can be used to detect carbohydrate malabsorption.[10](https://dm5migu4zj3pb.cloudfront.net/manuscripts/106000/106916/JCI72106916.pdf) A 1972 study established a quantitative relationship between the amount of carbohydrate delivered to the colon and the volume of hydrogen excreted in breath.[10](https://dm5migu4zj3pb.cloudfront.net/manuscripts/106000/106916/JCI72106916.pdf)\n\n**VOC analysis.** Breath volatiles arise from endogenous production, metabolism of ingested precursors, bacterial metabolism in gut or airways, and environmental exposure.[3](https://www.annualreviews.org/content/journals/10.1146/annurev-anchem-071213-020043) Typical levels are nitric oxide 10–50 ppb, ammonia 0.5–2 ppm, carbon monoxide 0–6 ppm, and methane 2–10 ppm.[9](https://iopscience.iop.org/article/10.1149/1945-7111/ab67a6)\n\n## How it is done\n\n**Urea breath test.** The patient fasts, then ingests 13C-urea, commonly 75 mg in 200 mL of citric acid solution; breath samples are taken at baseline and at 20–30 minutes, and a delta-over-baseline (DOB) above roughly 3.5–5‰ (parts per thousand) is positive.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/) • [19](https://pmc.ncbi.nlm.nih.gov/articles/PMC6807115/) DOB thresholds vary from 2.7 to 7 across laboratories and populations.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) The 14C version uses a 1-microcurie capsule after a 6-hour fast, with breath collected 10 minutes after ingestion.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) Before testing, antibiotics and bismuth are stopped for at least 4 weeks and PPIs or sucralfate for at least 2 weeks; eradication testing waits at least 4 weeks after treatment; antacids do not interfere.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) • [11](https://pmc.ncbi.nlm.nih.gov/articles/PMC10865822/)\n\n**Hydrogen/methane breath test.** For SIBO, the recommended substrates are lactulose 10 g or glucose 75 g in 300 mL water; for malabsorption, lactose 25 g or fructose 25 g.[8](https://www.bsg.org.uk/getattachment/d61ac8d5-a1f0-4a73-ad2e-ebdfde4a1a2c/AGIP-Best-Practice-Statement-for-HMBT_24-01-19.pdf?lang=en-US) Breath is sampled at least every 15 minutes, for at least 2 hours in SIBO studies and at least 3 hours for malabsorption.[8](https://www.bsg.org.uk/getattachment/d61ac8d5-a1f0-4a73-ad2e-ebdfde4a1a2c/AGIP-Best-Practice-Statement-for-HMBT_24-01-19.pdf?lang=en-US) Preparation includes avoiding antibiotics for 4 weeks, fermentable foods for 24 hours, a 12-hour fast, and no smoking on the test day.[8](https://www.bsg.org.uk/getattachment/d61ac8d5-a1f0-4a73-ad2e-ebdfde4a1a2c/AGIP-Best-Practice-Statement-for-HMBT_24-01-19.pdf?lang=en-US)\n\n## Origin\n\nThe hydrogen work began when [Michael D. Levitt](https://www.edgepedia.org/michael-d-levitt) reported the production and excretion of hydrogen gas in man in the New England Journal of Medicine in 1969.[12](https://doi.org/10.1056/nejm196907172810303) A breath-hydrogen test for small-intestinal bacterial colonization was reported by Geoffrey Metz and colleagues in [The Lancet](https://www.edgepedia.org/the-lancet) in 1976 [13](https://doi.org/10.1016/s0140-6736%2876%2992779-3), and the lactulose hydrogen breath test for small-bowel bacterial overgrowth by J. M. Rhodes and colleagues in the Scandinavian Journal of Gastroenterology in 1979.[14](https://doi.org/10.3109/00365527909179892) The 13C-urea breath test was reported by David Y. Graham and colleagues in The Lancet in 1987 [15](https://doi.org/10.1016/s0140-6736%2887%2992145-3), and standardized methodology for H2-breath testing was consolidated in the 2009 Rome Consensus Conference led by A. Gasbarrini and colleagues.[16](https://doi.org/10.1111/j.1365-2036.2009.03951.x) On the VOC side, an analysis found breath contains no fewer than 200 VOCs; breath is now known to contain more than 3500.[9](https://iopscience.iop.org/article/10.1149/1945-7111/ab67a6)\n\n## Variants\n\n**13C versus 14C UBT.** Both isotopes are FDA-approved and perform similarly, with sensitivities above 95% and specificities above 93%.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) The 14C test delivers about 1 microcurie, roughly 24 hours of natural background radiation, so the non-radioactive 13C test is preferred in young children and pregnant women.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) • [5](https://www.mdpi.com/2075-4418/12/10/2428) A simplified single-sample protocol using 50 mg 13C-urea, no test meal, and one breath sample at 10 minutes has been reported with 100% accuracy for H. pylori diagnosis.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/)\n\n**Hydrogen plus methane.** Adding methane measurement captures the 20–30% of people whose main fermentation product is methane, improving diagnostic accuracy [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/); about 20% of patients are methane producers, more in chronic constipation.[8](https://www.bsg.org.uk/getattachment/d61ac8d5-a1f0-4a73-ad2e-ebdfde4a1a2c/AGIP-Best-Practice-Statement-for-HMBT_24-01-19.pdf?lang=en-US)\n\n**Electronic nose and VOC platforms.** An eNose combines a sensor array, signal processing, and pattern recognition; metal oxide semiconductor sensors detect VOCs through temperature- and dopant-tunable conductivity changes.[4](https://www.mdpi.com/2304-6732/12/9/848) Mass spectrometric techniques include SIFT-MS, which uses H₃O⁺, NO⁺, and O₂⁺ reagent ions, and PTR-MS with pptv-level real-time detection.[9](https://iopscience.iop.org/article/10.1149/1945-7111/ab67a6) Machine-learning classifiers reach 93% accuracy for cancer in published datasets, but clinical adoption is limited by sampling standardization, sensor drift, and the lack of large-scale validation in diverse cohorts.[17](https://iopscience.iop.org/article/10.1088/1752-7163/ac5230) • [4](https://www.mdpi.com/2304-6732/12/9/848)\n\n## Applications\n\nUBT is used to detect H. pylori infection and to confirm eradication after treatment.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) Published UBT accuracy estimates differ by dataset. A 41-study meta-analysis found study-level sensitivities of 64–100% and specificities of 60.5–100%, with pooled sensitivity 92.5% and specificity 89.9%, and heterogeneity near \\( I^{2} \\approx 98\\% \\).[5](https://www.mdpi.com/2075-4418/12/10/2428) Against gastric culture or urease tests, UBT sensitivity and specificity range from 94–99% and 93–100% [11](https://pmc.ncbi.nlm.nih.gov/articles/PMC10865822/), and European meta-analyses confirm ≥95% for both in adults and children.[18](https://rcastoragev2.blob.core.windows.net/ab62c0abbbaf14111905ab98602a7c61/PMC8259225.pdf)\n\nHydrogen and methane breath tests are used for SIBO and for lactose and [fructose malabsorption](https://www.edgepedia.org/fructose-malabsorption).[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/) The glucose hydrogen breath test at a 12 ppm cutoff shows 62% sensitivity and 83% specificity against jejunal aspirate culture.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/) A meta-analysis of 14 studies found a cutoff below 20 ppm gave pooled sensitivity 61.7% and specificity 86.0%, better than the ≥20 ppm cutoff (47.3% and 80.9%).[6](https://www.jnmjournal.org/journal/view.html?doi=10.5056%2Fjnm25185)\n\n## Limitations and alternatives\n\n**Drug and condition effects.** UBT sensitivity falls 12–23% while patients take PPIs, with no effect from antacids; esomeprazole and lansoprazole cause more false negatives than omeprazole or pantoprazole, and the potassium-competitive blocker vonoprazan should presumably also be stopped 2 weeks before testing.[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC10865822/) False positive UBT results occur in achlorhydria, where urease-producing bacteria such as [Proteus mirabilis](https://www.edgepedia.org/proteus-mirabilis), [Citrobacter freundii](https://www.edgepedia.org/citrobacter-freundii), and [Staphylococcus aureus](https://www.edgepedia.org/staphylococcus-aureus) hydrolyze the urea, and from oral flora urease or Helicobacter heilmannii.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) Accuracy is lower in children (75–100%) and after gastric surgery, and recent upper GI bleeding can affect results.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) Some apparent false positives in comparison studies may reflect biopsy sampling error, since H. pylori colonization is discontinuous.[5](https://www.mdpi.com/2075-4418/12/10/2428)\n\n**Hydrogen test pitfalls.** False negatives follow recent antibiotic use, lung disorders, or hydrogen non-production, seen in about 10–20% of patients; false positives follow recent smoking or inadequate fasting.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/)\n\n**Alternatives.** UBT and the stool antigen test are the most reliable noninvasive H. pylori methods; stool antigen testing is less expensive with sensitivity and specificity above 93%.[1](https://www.ncbi.nlm.nih.gov/books/NBK542286/) [Serology](https://www.edgepedia.org/serology) cannot distinguish active from remote infection, so guidelines avoid it; direct urease testing of gastric specimens reaches 90% sensitivity and at least 95% specificity.[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC10865822/) UBTs do not provide antimicrobial susceptibility data.[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC10865822/) For SIBO, jejunal aspirate culture, the reference standard, itself produces false positives through oral contamination and false negatives through patchy bacterial distribution or non-cultivable species.[7](https://link.springer.com/article/10.1007/s10620-022-07487-8)\n\n## References\n\n1. [Urea Breath Test - StatPearls - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK542286/)\n2. [Update on diagnostic value of breath test in gastrointestinal and liver diseases](https://pmc.ncbi.nlm.nih.gov/articles/PMC4981765/)\n3. [Analysis of Exhaled Breath for Disease Detection (Annual Review of Analytical Chemistry)](https://www.annualreviews.org/content/journals/10.1146/annurev-anchem-071213-020043)\n4. [Exhaled Breath Analysis (EBA): A Comprehensive Review of Non-Invasive Diagnostic Techniques for Disease Detection (Photonics, 2025)](https://www.mdpi.com/2304-6732/12/9/848)\n5. [Systematic Review and Meta-Analysis on the Sensitivity and Specificity of 13C/14C-Urea Breath Tests in the Diagnosis of Helicobacter pylori Infection](https://www.mdpi.com/2075-4418/12/10/2428)\n6. [Hydrogen and Methane Breath Test: The Asian Neurogastroenterology and Motility Association Monograph (2025)](https://www.jnmjournal.org/journal/view.html?doi=10.5056%2Fjnm25185)\n7. [Performance and Interpretation of Hydrogen and Methane Breath Testing: Impact of North American Consensus Guidelines (Digestive Diseases and Sciences, 2022)](https://link.springer.com/article/10.1007/s10620-022-07487-8)\n8. [AGIP Proposed Standardised Testing Protocol for Hydrogen/Methane Breath Testing (British Society of Gastroenterology)](https://www.bsg.org.uk/getattachment/d61ac8d5-a1f0-4a73-ad2e-ebdfde4a1a2c/AGIP-Best-Practice-Statement-for-HMBT_24-01-19.pdf?lang=en-US)\n9. [Review, Non-Invasive Monitoring of Human Health by Exhaled Breath Analysis: A Comprehensive Review (J. Electrochem. Soc.)](https://iopscience.iop.org/article/10.1149/1945-7111/ab67a6)\n10. [Use of Pulmonary Hydrogen (H2) Measurements to Quantitate Carbohydrate Absorption (Journal of Clinical Investigation, 1972)](https://dm5migu4zj3pb.cloudfront.net/manuscripts/106000/106916/JCI72106916.pdf)\n11. [Testing for Helicobacter pylori in an era of antimicrobial resistance (J Clin Microbiol, February 2024)](https://pmc.ncbi.nlm.nih.gov/articles/PMC10865822/)\n12. [Michael D. Levitt (1969). Production and Excretion of Hydrogen Gas in Man. New England Journal of Medicine.](https://doi.org/10.1056/nejm196907172810303)\n13. [BREATH-HYDROGEN TEST FOR SMALL-INTESTINAL BACTERIAL COLONISATION (The Lancet, 1976)](https://doi.org/10.1016/s0140-6736%2876%2992779-3)\n14. [J. M. Rhodes, P. Middleton, D. P. Jewell (1979). The Lactulose Hydrogen Breath Test as a Diagnostic Test for Small-Bowel Bacterial Overgrowth. Scandinavian Journal of Gastroenterology.](https://doi.org/10.3109/00365527909179892)\n15. [CAMPYLOBACTER PYLORI DETECTED NONINVASIVELY BY THE 13C-UREA BREATH TEST (The Lancet, 1987)](https://doi.org/10.1016/s0140-6736%2887%2992145-3)\n16. [A Gasbarrini and colleagues (2009). Methodology and Indications of H2‐Breath Testing in Gastrointestinal Diseases: the Rome Consensus Conference. Alimentary Pharmacology & Therapeutics.](https://doi.org/10.1111/j.1365-2036.2009.03951.x)\n17. [Volatile compounds in human breath: critical review and meta-analysis (Journal of Breath Research)](https://iopscience.iop.org/article/10.1088/1752-7163/ac5230)\n18. [European guideline on indications, performance and clinical impact of 13C-breath tests (EAGEN, ESNM, ESPGHAN consensus)](https://rcastoragev2.blob.core.windows.net/ab62c0abbbaf14111905ab98602a7c61/PMC8259225.pdf)\n19. [pmc.ncbi.nlm.nih.gov](https://pmc.ncbi.nlm.nih.gov/articles/PMC6807115/)\n\n---\n*Topic: Encyclopedia › Life and health › Human health and medicine › Clinical assessment and procedures › Diagnosis and clinical assessment › Laboratory and in-vitro diagnostics › Genetic and genomic testing*\n\n*Initially written Sep 29, 2026 · Edited: Oct 15, 2026; Oct 25, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n", "same_as": [], "url": "https://www.edgepedia.org/breath-test", "markdown_url": "https://www.edgepedia.org/breath-test.md", "license": { "name": "Edgepedia Community License 1.0", "url": "https://www.edgepedia.org/edgepedia/license", "summary": "Free with credit, commercial use included. AI training is open to everyone. For other uses, organizations over USD 100M in revenue or 100M monthly users license separately.", "spdx": "LicenseRef-Edgepedia-Community-1.0" }, "credit": "\"Breath test\", Edgepedia (EdgeChat), https://www.edgepedia.org/breath-test. Edgepedia Community License 1.0.", "credit_md": "\"[Breath test](https://www.edgepedia.org/breath-test)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/breath-test](https://www.edgepedia.org/breath-test). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"Breath test\", Edgepedia (EdgeChat), https://www.edgepedia.org/breath-test. Edgepedia Community License 1.0.", "speakable": "A breath test measures gases in exhaled breath to detect disease, chiefly the urea breath test for H. pylori and hydrogen tests for malabsorption and SIBO." }