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SIBO

Designed for a 60-second scan in primary care. Use this to explain why this theory fits, what would weaken it, and which tests are most worth discussing.

Why this still fits

My brain fog gets worse after eating, especially when it comes with bloating and gut symptoms. I want to discuss whether SIBO testing fits before trying to guess with treatment alone.

What would weaken it

  • -No meal timing pattern and no bloating, gas, or bowel symptoms traveling with the fog.
  • -Normal testing plus a story that fits anxiety, sleep disruption, or food sensitivity better than bacterial overgrowth.
  • -No relationship between symptom severity and fermentable foods or digestion.

Key points to communicate

  • •I want to know whether breath testing makes sense before empiric treatment.
  • •If this is not SIBO, please tell me whether gut dysbiosis, reflux, IBS, or food sensitivity fits better.
  • •If testing is positive, I also want to discuss recurrence risk and underlying motility issues.

Bring this to the visit

  • •Breath test results if done: hydrogen, methane, and hydrogen sulfide.
  • •A list of GI symptoms with timing relative to meals.
  • •Prior antibiotic or herbal antimicrobial treatment history with response.
  • •Current diet, prokinetic use, and any motility testing results.

Useful screening structure

  • -Lactulose or glucose breath test for hydrogen and methane SIBO.
  • -Trio-Smart breath test if hydrogen sulfide SIBO is suspected.
  • -Celiac panel to rule out celiac before attributing everything to SIBO.

Tests and measurements to discuss

SIBO breath test (lactulose or glucose) - I understand the North American Consensus recommends specific cutoffs

What this helps clarify: Screens for small intestinal bacterial overgrowth

Range context

Negative for H₂/CH₄ rise

How to use the result

Save the result with date and symptoms from the same week.

Trio-Smart test if hydrogen sulfide SIBO (ISO) is suspected

What this helps clarify: Advanced at-home breath test measuring hydrogen, methane, AND hydrogen sulfide to distinguish SIBO, IMO, and ISO subtypes.

Range context

H₂, CH₄, H₂S thresholds

How to use the result

Save the result with date and symptoms from the same week.

B12, ferritin, and fat-soluble vitamins to check for malabsorption

What this helps clarify: Iron storage marker that can affect energy, focus, and cognition.

Range context

40-100 ng/mL

How to use the result

Save the result with date and symptoms from the same week.

Consider whether underlying causes should be evaluated (see below)

Questions to ask directly

  • •Is SIBO the root cause of my fog, or is it downstream of another condition like hypothyroidism?
  • •Should I try rifaximin, herbal antimicrobials, or an elemental diet?
  • •What prokinetic strategy prevents recurrence after clearing SIBO?
  • •Could this be SIFO (fungal) rather than SIBO, especially if antibacterials have not helped?

Functional impact snapshot

  • -Track fog severity against meal timing and composition.
  • -Rate cognitive function during antimicrobial treatment to detect improvement.
  • -Note recurrence pattern: how many weeks after treatment clearing before symptoms return?

Escalate instead of self-managing if

  • •Severe malnutrition or significant weight loss despite eating.
  • •Obstruction symptoms: severe bloating, vomiting, inability to pass gas.
  • •Blood in stool or iron deficiency anemia requiring colonoscopy.

Peer-reviewed references

  1. 1. HTTPS://JOURNALS.LWW.COM/AJG/FULLTEXT/2020/02000/ACG_CLINICAL_GUIDELINE__SMALL_INTESTINAL_BACTERIAL.9.ASPX [DOI]
  2. 2. Rezaie et al., Am J Gastroenterol, 2017 - North American Consensus on breath testing (PMID 28323273) [DOI]
  3. 3. Pimentel et al., NEJM, 2011 - Rifaximin for IBS without constipation (PMID 21208106) [DOI]