SIBO — What It Is, Why Your IBS Diagnosis Is Probably Wrong, and the 90-Day Protocol That Actually Works

SIBO — What It Is, Why Your IBS Diagnosis Is Probably Wrong, and the 90-Day Protocol That Actually Works

If your bloating gets worse as the day goes on, if "eat more fiber" advice has made you feel worse, and if antibiotics gave you a few weeks of relief before everything came back — your IBS diagnosis is probably wrong.

What you actually have is more likely SIBO — small intestinal bacterial overgrowth. It's the most under-diagnosed gut condition in America. Roughly 60% of patients carrying an "IBS" diagnosis meet criteria for SIBO when properly tested. Most never get tested. They get a low-FODMAP handout, a refill of antispasmodics, and a doctor visit that ends with "we'll keep an eye on it."

This is the post I wish someone had handed me at 23, when I was bloated every evening and my GI worked through a structural workup that ruled out cancer, IBD, and celiac — and then stopped. Below is what SIBO actually is, the three subtypes (and which one you have), why it keeps coming back, and the 90-day, four-phase protocol that actually addresses the root cause instead of just suppressing symptoms.

Venn diagram showing how SIBO is a subset of patients diagnosed with IBS, with shared and distinguishing symptoms "IBS"diagnosis of exclusionSIBOtestable, treatable~60% OVERLAPwhen IBS isproperly testedstress-driven,post-viral,other functionaltested viabreath testing,treated by phaseMost "IBS" labels are SIBO that hasn't been tested for.

Most "IBS" labels are SIBO that hasn't been tested for.

The most under-diagnosed gut condition in America

SIBO is what's actually behind a large fraction of cases that get labeled "IBS." Your doctor probably doesn't test for it. The standard test, when ordered, has well-documented sensitivity issues. And the standard treatment doesn't address why the overgrowth happened in the first place.

The numbers worth knowing:

  • ~60% — share of IBS patients who meet criteria for SIBO when properly tested (Pimentel et al., Am J Gastroenterol).
  • 10⁵+ CFU/mL — the bacterial threshold that defines SIBO. A healthy small intestine runs about 10³ CFU/mL. SIBO is roughly 100× that density (Rezaie et al., 2017 ACG consensus).
  • ~70% — relapse rate within 9–12 months after a single course of rifaximin alone (Lauritano et al., Am J Gastroenterol). Antibiotics work in the moment. They don't address why.
  • 90 minutes — the interval at which the migrating motor complex (MMC) should fire to sweep the small intestine clean. When it doesn't, bacteria accumulate (Vantrappen et al., JCI).

If antibiotics gave you temporary relief and your IBS came back, the diagnosis was wrong.

Why your doctor will give you the wrong diagnosis

The IBS catch-all bucket. "IBS" is a diagnosis of exclusion. Most GI workups stop before they reach SIBO testing — leaving up to 60% of IBS labels masking the real cause.

The breath test problem. The lactulose breath test has documented false-negative rates. The glucose breath test only catches proximal SIBO. Most clinics order one, not both, and read them with outdated cutoffs.

The standard antibiotic failure. Rifaximin works in the moment but doesn't address motility, stomach acid, or the ileocecal valve dysfunction underneath the overgrowth. Without addressing those, relapse is the default — not the exception.

GI specialists are trained on structural disease. SIBO is a functional, motility-driven condition. Specialists rule out cancer, IBD, celiac — and stop there.

Is it IBS or SIBO? The 5-question filter

Five questions. Three or more "yes" answers and SIBO becomes the more likely diagnosis. This isn't a substitute for testing — it's a filter for whether testing is worth pursuing.

  1. Does your bloating get worse as the day goes on? Classic SIBO pattern: flat stomach in the morning, visibly distended by evening. The bacterial population fermenting your food expands as you eat throughout the day.
  2. Do high-fiber or high-FODMAP foods make your symptoms worse — not better? Healthy gut bacteria thrive on fiber. SIBO bacteria over-ferment it, producing the gas that drives bloating, pain, and altered bowel habits. If "eat more fiber" advice has made you worse, that's diagnostic.
  3. Did your symptoms start after a stomach bug, food poisoning, or traveler's diarrhea? Post-infectious SIBO is well-documented. A single bout of gastroenteritis can disrupt the migrating motor complex permanently, opening the door to overgrowth months or years later.
  4. Have antibiotics ever given you temporary relief, then symptoms returned? The strongest single signal. Antibiotics knocking back symptoms means there's a bacterial driver. Symptoms returning means the underlying motility/acid issue was never addressed.
  5. Do you have brain fog, fatigue, or skin issues alongside the gut symptoms? SIBO produces endotoxins and metabolites that cross the gut wall and affect the brain, immune system, and skin. The "I'm bloated AND foggy AND broken out" cluster is highly suggestive.

What's actually happening in your small intestine

Most of your gut bacteria live in your colon — by design. Your small intestine should be relatively sparse, with bacteria around 1,000× lower in concentration. SIBO is what happens when that ratio inverts.

GI tract bacterial concentration: low in stomach and small intestine, high in colon — and what happens when it inverts in SIBO HEALTHY GI TRACT — BACTERIAL DENSITYStomach10¹–10³Small Intestine~10³ CFU/mLColon10¹¹⁺ CFU/mL — by designSIBO — THE INVERSIONStomachoften low acidSmall Intestine10⁵–10⁹ CFU/mL — overgrowthColonnormal densityBacteria that belong downstream have migrated upstream — into the absorptive zone wherethey ferment your meals before your body can absorb the nutrients.SIBO threshold: ≥10⁵ CFU/mL in the small intestine · 100× the normal density

The small intestine is where you digest and absorb food. When bacteria overgrow there, they get to your meals before your enzymes do. They ferment what you eat — producing hydrogen, methane, or hydrogen sulfide gas as byproducts. That gas is what drives the bloating, the distension, the food sensitivities. And the bacterial metabolites disrupt the gut lining, leak across into circulation, and produce the systemic symptoms most patients have given up on linking to their gut.

Why the overgrowth happens — the four root causes

SIBO almost never happens in isolation. There's always an upstream failure. Treat the bacteria without addressing the root cause and you get a textbook 70% relapse rate. The four root causes that drive almost every case:

  1. Slowed migrating motor complex (MMC). The cleansing wave that's supposed to sweep the small intestine clean every 90 minutes between meals. When it stops firing, bacteria accumulate.
  2. Low stomach acid. Acid is the first line of defense against ingested bacteria. PPI use, age, and chronic stress all suppress it — letting bacteria pass through alive.
  3. Ileocecal valve dysfunction. The one-way valve between small and large intestine. When it fails, colon bacteria flow backward into the small intestine.
  4. Post-infectious origin. Food poisoning produces antibodies that cross-react with the gut's own pacemaker cells (vinculin auto-antibodies). The MMC is impaired permanently — and overgrowth follows.

How SIBO breaks your gut over time

Healthy fermentation in the colon produces beneficial short-chain fatty acids; SIBO fermentation in the small intestine produces gas, endotoxins, and inflammation HEALTHY — FERMENTATION IN THE COLONFiber + bacteria → short-chain fatty acids (butyrate, acetate, propionate)Fuels colon cells · regulates immune system · produces beneficial postbioticsSIBO — FERMENTATION IN THE WRONG PLACESame fiber + bacteria, wrong location → gas, endotoxins, acidic byproductsHydrogen · methane · hydrogen sulfide · LPS · disrupted absorptionHealthy foods feed bacteria. When the bacteria are in the colon (where they belong),fermentation produces beneficial short-chain fatty acids. When the bacteria have migratedupstream, fermentation produces gas, endotoxins, and acidic byproducts in the small intestine— exactly where you're trying to absorb your meal.The same fiber that's healthy in a normal gut becomes the fuel making you sick.

This is the healthy-food paradox. Patients with SIBO often describe doing "everything right" — eating clean, going low-carb, doing whole foods — and feeling worse. The reason is structural, not nutritional. The fermentation that should be happening downstream (in the colon, producing beneficial short-chain fatty acids) is happening upstream (in the small intestine, producing gas and endotoxins). The gut isn't broken. The bacteria are in the wrong place.

Untreated, this cascades. The fermentation byproducts and bacterial endotoxins damage the small intestine's lining (the brush border, where digestive enzymes live). Damaged brush border = damaged enzyme production = inability to break down lactose, fructose, certain proteins. Now you have food intolerances on top of the SIBO. Most patients arrive at the SIBO diagnosis with a list of foods they "can't eat" — that list is the consequence, not the cause.

Three subtypes — and which one you have

SIBO is three conditions, not one. Different organisms, different metabolic byproducts, different symptoms, different treatments. The gas pattern is the diagnostic — and the treatment lever.

Gas production pathways for the three SIBO subtypes: hydrogen, methane, hydrogen sulfide GAS PRODUCTION PATHWAYSHydrogenH₂Bacteria: E. coli, KlebsiellaSymptoms: bloating + diarrheaMost common subtypeTreatment levers:rifaximin · oregano oilberberineMethane (IMO)CH₄Archaea: M. smithiiSymptoms: bloating + constipationSluggish bowels, weight gainTreatment levers:rifaximin + neomycinberberine + allicinHydrogen SulfideH₂SSRB: DesulfovibrioSymptoms: rotten-egg gasOften missed by standard testingTreatment levers:low-sulfur · bismuthberberineEach subtype produces a different gas — and standard breath tests only catch two of the three.Berberine is the through-line: documented activity across all three subtypes.

Hydrogen SIBO is the most common form. Bacteria like E. coli and Klebsiella ferment carbohydrates and produce hydrogen gas. Classic presentation: bloating + diarrhea. Standard rifaximin protocols are designed around this subtype.

Methane (intestinal methanogen overgrowth, or IMO) is technically not bacteria — it's archaea, a separate domain of life. Methanobrevibacter smithii consumes hydrogen and produces methane. Methane slows gut motility, which means the classic presentation is bloating + constipation, sometimes with stubborn weight gain. Antibiotics that work on bacteria often miss archaea entirely.

Hydrogen sulfide SIBO is the dark horse — most labs didn't even test for it until recently. Sulfate-reducing bacteria like Desulfovibrio produce H₂S, which has a rotten-egg smell and damages the gut lining directly. If you're sulfur-sensitive, can't tolerate eggs/cruciferous veg/garlic, this is likely your subtype.

How berberine 500mg targets each subtype

Berberine is an isoquinoline alkaloid found across multiple plants — barberry root, goldenseal, Oregon grape, coptis. It's structurally unusual for a plant compound: yellow, fluorescent, with a positive charge that lets it cross bacterial membranes by exploiting the cell's normal electrochemistry. That charge is part of why it's effective across multiple SIBO subtypes — but the mechanisms differ for each one.

Berberine mechanism: a single molecule disrupting hydrogen-producing bacteria, methanogen archaea, and sulfate-reducing bacteria BERBERINE 500MG · CLINICAL DOSEberberineHydrogen producersmembrane disruption ·DNA gyrase inhibitionMethanogen archaeamethanogenesis pathwaydisruption · F420 inhibitionSulfate-reducing bacteriapositive charge crosses outermembrane · halts H₂S production

In a Johns Hopkins-affiliated comparative study, herbal antimicrobial protocols centered on berberine showed response rates equivalent to rifaximin — the conventional gold-standard antibiotic — for normalizing breath test values in SIBO patients. The herbal protocol also covered methane and hydrogen sulfide subtypes that rifaximin alone misses. Most importantly, broader spectrum coverage tends to translate to lower relapse rates over the 6–12 month window after kill-phase treatment ends.

The dose matters more than people realize. Below 200mg per dose: subclinical. At 400–500mg twice daily: the well-documented antimicrobial range used in clinical SIBO studies. Most over-the-counter "berberine for blood sugar" products dose at 200mg or less — which works for metabolic effects but is below the antimicrobial threshold for SIBO.

When SIBO is also SIFO

SIBO doesn't always travel alone. In a meaningful percentage of cases, the small intestine is overgrown with both bacteria and fungi — typically Candida albicans. This is SIFO: small intestinal fungal overgrowth. The symptoms overlap heavily with SIBO and you can have both simultaneously.

Two-circle Venn diagram showing SIBO and SIFO overlap SIBObacterial overgrowthSIFOfungal overgrowthCO-INFECTIONCommonWhy the protocol covers both — antibacterial and antifungal in the same formula.

Signs SIFO is part of the picture: oral thrush, recurrent yeast infections, sugar/carb cravings that feel uncontrollable, white-coated tongue, intense brain fog disproportionate to your gut symptoms, sensitivity to alcohol or vinegar. If three or more of these are present alongside SIBO symptoms, treatment that covers only bacteria will leave the fungal piece untreated — and your symptoms partially better but not resolved.

This is why a serious SIBO protocol covers both. Treating bacteria with antimicrobials creates ecological space that Candida opportunistically fills. The protocol that addresses this from the start has fewer "I felt better for two weeks then crashed" failures.

The MMC: why fasting matters mechanically

The migrating motor complex (MMC) is the single most-overlooked piece of SIBO recovery. It's the cleansing wave that fires in the small intestine roughly every 90 minutes — but only between meals and at night, in the fasted state. When you snack constantly, the MMC is suppressed indefinitely.

The migrating motor complex 90-minute cycle: cleansing wave only fires between meals in the fasted state THE MMC SWEEP CYCLEMeal endsPhase I (rest)Phase II (irregular)Phase III sweepCycle restartsA 90-minute cycle in the fasted statePhase III is the powerful cleansing wave that pushes residual bacteria downstream into the colon.Eat anything — even a snack — and the cycle resets to Phase I.No fasting between meals = no MMC = bacterial accumulation by default.

This is why the protocol calls for 4–5 hours between meals and a 14-hour overnight fast. Not for weight loss — for mechanics. You're letting your MMC fire long enough, often enough, to actually clear the small intestine. A patient who's eating every 2 hours "to keep blood sugar stable" is structurally preventing the very mechanism that should be sweeping their gut clean.

The 90-day, four-phase protocol

The 90-day SIBO protocol four phases: kill, heal, repopulate, prevent relapse THE 90-DAY PROTOCOLPhase 01 · KillDays 1–30Phase 02 · HealDays 14–60Phase 03 · RepopulateDay 45 onwardsPhase 04 · PreventDay 60 → lifelongThe phases overlap by design — heal begins while kill is still active,repopulation starts while heal is still active.

Phase 01 — Kill (Days 1–30)

The antimicrobial phase. The goal is to knock the bacterial overgrowth back below the symptomatic threshold while you address the root cause that let it happen in the first place. Microbiome Balance Formula at 1 pouch (8 capsules) with breakfast and 1 pouch with dinner — the 500mg berberine per dose lands in the documented clinical antimicrobial range. Hold the line on 4–5 hours between meals.

Phase 02 — Heal (Days 14–60)

The brush-border repair phase. Starts during the kill phase because the intestinal lining can begin healing the moment bacterial pressure drops — you don't have to wait. The L-glutamine 750mg, 200:1 aloe vera concentrate, marshmallow root, and slippery elm in Microbiome Balance Formula are doing the heal-phase work in parallel with the antimicrobials. That's why the phases overlap.

Phase 03 — Repopulate (Day 45 onwards)

Once the overgrowth is cleared and the lining is rebuilding, the right bacteria need to take up residence. The 10-strain probiotic blend (8 Lactobacillus + 2 Bifidobacterium) plus FOS prebiotic in Microbiome Balance Formula does the repopulation work without needing a separate product. This is the phase where most over-the-counter "SIBO protocols" fail — they kill but never reseed.

Phase 04 — Prevent Relapse (Day 60 → lifelong)

The 70% relapse rate isn't bad luck — it's the predictable outcome of stopping treatment without addressing the upstream motility/acid issues that caused the overgrowth originally. Maintenance is: 14-hour overnight fast nightly, 4–5 hours between meals, prokinetics (ginger before bed), and Microbiome Balance Formula at a 1-pouch maintenance dose for ongoing motility and gut-lining support.

A typical day on the protocol

A typical day on the SIBO protocol: three meals at 4-5 hour intervals, two doses of Microbiome Balance Formula, 14-hour overnight fast A TYPICAL DAY8amBreakfast+ MB pouch12:30pmLunch6pmDinner+ MB pouch10pmSleep4.5 hours · MMC fires ×35.5 hours · MMC fires ×314-hour overnight fast: 6pm → 8am next morning

Three meals. Two pouches of Microbiome Balance Formula (one with breakfast, one with dinner). Nothing else between meals — black coffee and water are fine; calories are not. Last meal by 6–7pm. First meal at 8am the next morning. That's a 14-hour overnight fast, and it's where most of your MMC sweeps will happen.

If you want the printable version

I built a free PDF that walks through the full 5-question self-assessment, the four root causes, the four-phase protocol, and a print-and-bring-to-your-doctor checklist for breath testing. Drop your email and I'll send it:

→ Download the SIBO Self-Assessment + Protocol Guide

What I personally take

I built Luna Lab around the formulas I wanted to take but couldn't find. For SIBO, that meant a single product that covers all four phases — kill, heal, repopulate, and prevent — in one pouch, dosed at the actual clinical thresholds. Not 200mg of berberine "for blood sugar." Not a probiotic-only product that ignores the kill phase. Not three separate bottles you're cycling through and forgetting.

Microbiome Balance Formula is the assembly: 500mg berberine per dose, NAC and ginger for the antimicrobial phase, L-glutamine 750mg + 200:1 aloe + marshmallow root + slippery elm for the heal phase, a 10-strain probiotic + FOS prebiotic for repopulation. Two pouches a day for the 90-day protocol; one pouch for maintenance after.

I run the full protocol twice a year. Take it or don't. The framework above is the framework whether you build the protocol from individual components or use Luna Lab.

Frequently Asked Questions

What is the difference between SIBO and IBS?

"IBS" is a diagnosis of exclusion — a label applied when other conditions are ruled out and a specific cause isn't found. SIBO is a specific, testable condition: bacterial overgrowth in the small intestine, defined as ≥10⁵ CFU/mL. Roughly 60% of patients labeled with IBS meet criteria for SIBO when properly tested. IBS is often the wrong label; SIBO is often the right diagnosis.

What is the most accurate test for SIBO?

The gold standard is small bowel aspirate culture — direct sampling of the small intestine — but it's invasive and rarely done. The clinical standard is the breath test (lactulose or glucose), which measures hydrogen and methane gas after a sugar challenge. Hydrogen sulfide testing is newer (Trio-Smart and similar) and required to catch the H2S subtype. The 2017 ACG consensus paper has the current cutoffs.

How long does it take to treat SIBO?

The kill phase typically runs 4–6 weeks. Symptoms often improve within the first 2 weeks, but stopping early is the most common reason for relapse. The full 90-day protocol gives the gut lining time to heal, the microbiome time to repopulate, and the migrating motor complex time to re-establish a functional rhythm. Severe cases can extend to 4–6 months.

Can SIBO come back after treatment?

Yes — and it's the default outcome if the underlying cause isn't addressed. The 70% relapse rate within 9–12 months after rifaximin alone (Lauritano et al.) is a textbook illustration. Relapse prevention requires addressing what caused the overgrowth in the first place: low stomach acid, slowed migrating motor complex, ileocecal valve dysfunction, or post-infectious vinculin auto-antibodies. Maintenance fasting, prokinetics, and ongoing gut support cut the relapse rate substantially.

Does berberine actually work for SIBO?

The Johns Hopkins-affiliated Chedid et al. study compared herbal antimicrobials (centered on berberine, oregano, and other botanicals) head-to-head with rifaximin for SIBO and found equivalent response rates. Berberine specifically has documented activity across all three SIBO subtypes — hydrogen, methane, and hydrogen sulfide — which is broader than rifaximin's spectrum. The dose matters: clinical SIBO studies use 400–500mg twice daily, not the 100–200mg in most over-the-counter products.

What should I eat during SIBO treatment?

The most important rule: eat actual meals, 4–5 hours apart, with a 14-hour overnight fast. The food matters less than the spacing — your migrating motor complex (the cleansing wave that sweeps your small intestine) only fires in the fasted state. Constant snacking suppresses it indefinitely. Diet protocols (low-FODMAP, SIBO-specific carbohydrate diet, biphasic) provide symptom relief during treatment but don't kill the overgrowth on their own.

Sources

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