Probiotic Discontinuation Before SIBO Breath Testing
You should discontinue probiotic supplements (like Align) for at least 2 weeks before SIBO breath testing, even if the lab instructions did not explicitly state this requirement. While probiotic-containing foods like yogurt and cottage cheese are less studied, the safest approach is to avoid all probiotic sources for 2 weeks prior to testing to prevent false-positive results.
Why This Matters
The most direct evidence comes from a controlled study showing that Bifidobacterium infantis 35624 (the strain in Align) significantly increases methane levels during lactulose breath testing after just 2 weeks of use 1. In this study:
- Methane levels rose significantly (p = 0.012) after probiotic administration
- The number of subjects with "abnormal" breath tests increased from 10 to 13 out of 19
- Three subjects had methane rises >20 ppm pre-probiotic, but six showed this post-probiotic
- Hydrogen levels were not affected, but methane elevations alone can lead to false SIBO diagnoses
This means probiotics can artificially elevate breath test gases to levels that would be interpreted as positive for SIBO, even in healthy individuals.
The Problem with Lab Instructions
The British Society of Gastroenterology guidelines acknowledge that "suggested approaches to diagnosis, how to undertake breath testing and how to interpret the results differ significantly between authorities" 2. Commercial lab instructions are not standardized and often incomplete. The fact that Genova Diagnostics did not mention probiotics in their preparation instructions represents a gap in their protocol, not evidence that probiotics don't matter.
Practical Recommendations
For probiotic supplements:
- Stop all probiotic capsules, tablets, and powders at least 2 weeks before testing
- This includes common brands like Align, Culturelle, and any multi-strain formulations
For probiotic-containing foods:
- While less studied than supplements, yogurt and cottage cheese contain live bacterial cultures
- The conservative approach is to avoid these for 2 weeks as well
- The bacterial load in foods is generally lower than supplements, but can still potentially affect results
Other pre-test considerations:
- Continue the dietary preparation (white rice, plain meat) as instructed
- Maintain the fasting period (your 22-27 hour fast was appropriate)
- Avoid antibiotics for 4 weeks before testing if possible
- Avoid laxatives and prokinetic medications
Why Guidelines Don't Always Specify This
The BSG guidelines note that "both glucose and lactulose hydrogen breath tests have poor sensitivity and specificity" 3. Because breath testing has inherent limitations, many guidelines focus on the substrate choice (glucose vs. lactulose) and interpretation criteria rather than comprehensive pre-test preparation. However, the research clearly demonstrates that probiotics alter test results 1, making their discontinuation a critical but often overlooked step.
What This Means for Your Test Results
If you took probiotics (including yogurt or cottage cheese) within 2 weeks of your test:
- Your results may show falsely elevated methane levels
- A positive result should be interpreted cautiously
- Consider retesting after proper probiotic discontinuation if clinical suspicion for SIBO remains high
- Alternatively, if symptoms strongly suggest SIBO, empirical treatment with rifaximin 550 mg twice daily for 1-2 weeks may be reasonable 2
The Bottom Line
Laboratory instructions are not comprehensive clinical guidelines. The research evidence is clear that probiotics affect breath test results 1. For accurate SIBO diagnosis, discontinue all probiotic supplements for 2 weeks and ideally avoid probiotic-rich foods during this period, regardless of what the lab's instruction sheet says or doesn't say.