Diagnostic Utility of Carbohydrate Breath Tests for SIBO, Fructose, and Lactose Intolerance



Unexplained bloating, gas, and pain are common symptoms. If routine tests are negative, such patients are often labeled as irritable bowel syndrome.


To determine the diagnostic utility of breath tests that assess for small intestinal bacterial overgrowth (SIBO), fructose or lactose intolerance, and the predictive value of symptoms.


Patients with gas, bloating, diarrhea, abdominal pain (≥ 6 months), and negative endoscopy and radiology tests were assessed with symptom questionnaires, glucose (75 g), fructose (25 g), or lactose (25 g) breath tests. Breath tests were categorized as positive when H2 (≥ 20 ppm) or CH4 (≥ 15 ppm) increased above baseline values or as hypersensitive when symptoms changed significantly without rise in H2/CH4 or as negative.


1230 patients (females = 878) underwent 2236 breath tests. The prevalence of SIBO was 33% (294/883), fructose intolerance was 34% (262/763), and lactose intolerance was 44% (260/590). Hypersensitivity was found in 16% and 9%, respectively, during fructose and lactose breath tests. Although gas (89%), abdominal pain (82%), and bloating (82%) were highly prevalent, pretest symptoms or their severity did not predict an abnormal breath test, but symptoms during the breath test facilitated diagnosis of SIBO, fructose, and lactose intolerance and hypersensitivity.


Approximately 45% of patients with unexplained gas and bloating had SIBO, fructose, or lactose intolerance; another 9–16% had visceral hypersensitivity. Pretest symptoms were poor predictors, but symptoms during the breath tests were useful. Breath tests are safe, provide significant diagnostic yield, and could be useful in routine gastroenterology practice.

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We thank Mrs. Helen Smith for the excellent secretarial assistance, and Mrs. Collier Badger, Mrs. Arie Mack and Mrs. Michelle Jackson for assistance with the breath tests. Dr. Rao was supported by NIH 5R21 DK104127-02 and U-34, DK109191-02.

Author information




SSCR was involved in study concept, patient recruitment, analysis of breath test, overall supervision, manuscript writing, IRB submission. MA-B helped in data analysis, data interpretation, manuscript writing. EC-A contributed to data analysis, data interpretation, IRB, statistical analysis. NR helped in data entry. BMD contributed to data entry.

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Correspondence to Satish S. C. Rao.

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The study was approved by the Augusta University Institutional Review Board No. 1114725 and registered at Clinical Trials Gov: NCTO 03261856.

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Amieva-Balmori, M., Coss-Adame, E., Rao, N.S. et al. Diagnostic Utility of Carbohydrate Breath Tests for SIBO, Fructose, and Lactose Intolerance. Dig Dis Sci 65, 1405–1413 (2020). https://doi.org/10.1007/s10620-019-05889-9

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  • Small intestinal bacterial overgrowth
  • Fructose intolerance
  • Lactose intolerance
  • Breath test
  • Diagnosis