Written and Medically Reviewed by Dr. Dan Wool, NMD
Arizona-Licensed Naturopathic Physician and Gastroenterology Specialist
Updated: October 13, 2026

Quick Summary

SIBO is an overgrowth of bacteria in the small intestine, where very few should live. The bacteria ferment food before you can absorb it. The gas they make causes bloating, pain, and diarrhea or constipation.
Antibiotics clear SIBO in most people, and it often returns. In one study, breath tests turned positive again in 44% of patients within nine months of successful treatment. Relapse is common enough to plan for.
In most of the patients I see, SIBO is the result of something else: a stalled cleaning wave, low stomach acid, slow transit, a structural problem, or the wrong treatment for the gas involved.
Lasting results come from clearing the overgrowth and then addressing the reason it formed. That means restoring motility, reviewing medications, supporting digestion, and checking the thyroid before reaching for another round of antibiotics.

Mark (not his real name) was 47 and owned two restaurants. He had just finished his third round of rifaximin in 18 months. Each time the bloating vanished for a couple of months, and each time it crept back until he was loosening his belt by mid-afternoon.

He had taken omeprazole every morning for eight years. He also tasted food all day at work, so his gut rarely went an hour without something in it.

Nobody had asked about either habit. In my Scottsdale practice, that's the usual story with recurrent SIBO. The treatment worked. The reason the bacteria were there never got addressed.

What SIBO Is

SIBO stands for small intestinal bacterial overgrowth. Your colon is built to hold most of your gut bacteria. Your small intestine is built to hold very few, because that's where you absorb nutrients.

In SIBO, bacteria build up in the small intestine and ferment your food before you can absorb it [1].

Fermentation makes gas. The gas causes bloating, a belly that swells as the day goes on, belching, abdominal pain, and diarrhea or constipation [1]. More advanced cases can interfere with the absorption of fat and vitamin B12 [1].

SIBO and irritable bowel syndrome overlap heavily. One meta-analysis estimated that about 38% of people with IBS test positive for SIBO [2]. My IBS guide covers the other drivers worth checking.

Three Types of Overgrowth, Sorted by Gas

Breath testing sorts overgrowth by the gas the microbes make. The type matters because it changes the treatment.

Hydrogen-dominant SIBO

Bacteria ferment carbohydrates and release hydrogen. In my practice this type most often comes with loose stools and bloating that starts soon after meals.

What I look for: an early rise in hydrogen on breath testing.

Methane-dominant overgrowth (IMO)

Methane gas in the gut comes from archaea. Archaea are single-celled organisms distinct from bacteria, and they can live in the colon as well as the small intestine. For that reason the American College of Gastroenterology now calls this pattern intestinal methanogen overgrowth, or IMO [1]. Methane slows the gut and is associated with constipation [3].

What I look for: methane at or above 10 parts per million at any point during the test [1].

Hydrogen sulfide (H2S)

Some newer breath tests also measure a third gas, hydrogen sulfide (H2S). The research behind it is younger, so I read those results with more caution.

What I look for: symptoms that fit SIBO when hydrogen and methane are both unremarkable.

Warning Signs That Need a Conventional Workup First

Some symptoms point away from SIBO and toward disease. These need a scope, imaging, or urgent care. See your primary care doctor or a gastroenterologist promptly if you have any of these:

Blood in your stool, or black, tarry stools
Unintentional weight loss
Iron deficiency anemia
Symptoms that wake you from sleep
Fever with ongoing diarrhea
Trouble swallowing or persistent vomiting
A family history of colon cancer, inflammatory bowel disease, or celiac disease
New bowel changes that start after age 50

Conventional gastroenterology is very good at this part. I want it done before I treat anyone for bacterial overgrowth.

How SIBO Is Tested

The standard test to determine SIBO is a breath test. You drink a sugar solution, usually lactulose or glucose, and breathe into collection tubes at 20-minute intervals for 2-3 hours.

Human cells don't make hydrogen or methane. Gut microbes do. So a rise in those gases on your breath points to fermentation. A hydrogen rise of 20 parts per million or more above baseline within 90 minutes is considered positive for SIBO [1].

The breath test is imperfect, and I say so to every patient.

Breath testing depends on how fast the sugar travels. In someone with rapid transit, the sugar can reach the colon early, and the result looks like SIBO when it's ordinary colon fermentation [3]. Slow stomach emptying can hide a real overgrowth [3].

Preparation matters too. Recent antibiotics, laxatives, and the wrong meal the day before can all distort the result [1].

So I read a breath test alongside someone's history. A positive result in someone with Mark's story above means something. A borderline result in someone with no risk factors gets a second look.

Why Treatment Works and Then Stops Working

The standard treatment is rifaximin. It's an antibiotic that stays almost entirely inside the upper gut. It's FDA-approved for IBS with diarrhea (IBS-D), and doctors prescribe it off-label for SIBO. In a meta-analysis of 32 studies, rifaximin cleared SIBO in about 71% of patients [4]. That's a good drug doing its job.

The trouble shows up later. One study followed 80 patients whose SIBO had been cleared with rifaximin. Breath tests turned positive again in about 13% by three months, 28% by six months, and 44% by nine months [5]. Older age, a prior appendectomy, and long-term use of acid-blocking medication each raised the odds [5].

In many of the patients I see, SIBO is the result of something else that let bacteria settle where they don't belong. An antibiotic clears the overgrowth and leaves that something untouched.

So I see a lot of patients who have been on multiple rounds of the same drug or herbal protocols (yes, they can do this too. While these are actually working, they do not address the root cause of SIBO and this - with all the frustrating ups and downs - becomes a poor long term plan.

This is worth mentioning (because I say it a lot): SIBO is not a root cause. It is a diagnosis, which is good, because diagnoses have treatments. But really, SIBO is a symptom. That's how I want you to think about it.

7 Reasons SIBO Comes Back

1. The cleaning wave isn't running

Between meals, a wave of muscle contractions sweeps leftover food and bacteria down the small intestine. It's called the migrating motor complex (MMC), and eating switches it off. Constant snacking keeps it off. Mark's all-day tasting was a textbook example. A past bout of food poisoning may also weaken this wave, and I cover that research in my IBS guide.

2. Stomach acid is too low

Acid kills most of the bacteria you swallow. A meta-analysis found that people taking proton pump inhibitors had about 1.7 times the odds of SIBO compared with people who weren't taking them [6]. Some people need these medications long term. For everyone else, the prescription deserves a regular review with the clinician who wrote it. Here's how I think about tapering in root cause care.

3. Something is physically/structurally slowing the flow

Scar tissue from abdominal surgery, pouches in the wall of the small bowel, narrowed segments, and surgically altered anatomy can all create pockets where contents pool [1]. These need imaging and a gastroenterologist or surgeon. No supplement fixes them.

4. The gas was methane and the treatment was built for hydrogen

Methane producers respond differently. In a retrospective study, rifaximin combined with a second antibiotic called neomycin cleared methane in 87% of patients, far more than rifaximin managed alone [7]. If your breath test showed methane and you received rifaximin alone, a relapse is less surprising.

5. A condition or medication is slowing your gut

Low thyroid function, diabetes-related nerve damage, and connective tissue diseases such as scleroderma all slow intestinal movement and raise SIBO risk [1]. Opioid pain medications slow the gut as well. If the brake stays on, the bacteria come back.

6. Digestion is weak upstream

Bile and pancreatic enzymes break food down before bacteria can get to it. In my experience, patients with low enzyme output relapse faster until that's supported.

7. It wasn't only SIBO

Celiac disease, bile acid diarrhea, pancreatic insufficiency, and yeast overgrowth in the small intestine (SIFO) can all mimic SIBO or travel with it. When symptoms return quickly after a clean breath test, I widen the search.

The Hormone Connection

Thyroid hormone sets the pace of the gut. In one study, 54% of people with a history of hypothyroidism tested positive for SIBO, compared with 5% of healthy controls [8].

When I see recurrent SIBO alongside fatigue, cold intolerance, or constipation, I check a full thyroid panel. This is the gut-hormone axis running in the other direction: the hormone problem comes first and the gut problem follows.

Slower gut motility can also result from hormone changes, especially in women. Low progesterone in perimenopasue or hormones suppressed by oral birth control as well as conditions such as PCOS (PMOS) and endometriosis, all can affect or impair MMC function and slow motility, leading to bacteria fermentation and overgrowth.

My Five-Step Approach to Recurrent SIBO

Step 1. Confirm the diagnosis and rule out lookalikes

I review the original breath test, repeat it if the first one was poorly prepared, and screen for celiac disease and the other conditions in reason 7.

Step 2. Identify the gas and the driver

Hydrogen, methane, or both? Then the history: medications, surgeries, meal timing, thyroid symptoms, and what happened right before the symptoms began.

Step 3. Clear the overgrowth with the right tool

In my practice I choose among three tools, and the choice depends on the gas, the history, and your preference. Rifaximin has the largest body of evidence [4].

Herbal antimicrobials are a reasonable alternative. In a study at Johns Hopkins, 46% of patients on a four-week herbal protocol had a normal follow-up breath test, compared with 34% on rifaximin. The difference was not statistically significant [9].

I often use formulas built around oregano oil and berberine. An elemental diet is the third option. It's a liquid formula of pre-digested nutrients. In one study of 93 patients, 80% had a normal breath test after 14 days [10]. It's demanding, and I reserve it for stubborn cases.

Step 4. Restart the cleaning wave

I ask patients to space meals 4-5 hours apart and to stop eating a few hours before bed.

In my practice I often add a bedtime prokinetic after treatment. A prokinetic is an agent that stimulates the migrating motor complex.

A retrospective study found that low-dose prokinetics taken at night delayed the return of symptoms after antibiotic treatment [11]. Options include prescription and herbal agents, such as ginger, and the right one is worth discussing with your practitioner.

Step 5. Fix what's upstream, then retest

We review acid-blocking medication with your prescriber, treat the thyroid if it's low, support enzymes where they're needed, and widen the diet again.

A low FODMAP diet can calm symptoms during treatment, and I use it as a short-term tool. I retest after treatment to confirm the overgrowth has cleared.

For Mark, our plan had three parts his earlier rounds lacked: meal spacing, a supervised review and taper of his omeprazole, and a bedtime prokinetic after treatment.

SIBO Resource Directory

Every SIBO article on the site, grouped by what you're trying to figure out. For the full IBS, SIBO, and Functional GI hub, start with my IBS guide.

The Bottom Line on Recurrent SIBO

SIBO that returns after treatment is common, and it usually has an explanation. The antibiotic or herb clears the overgrowth. The lasting fix comes from finding what let it form: a stalled cleaning wave, low stomach acid, a slow gut, a structural problem, or a treatment that didn't match the gas. If you've been through two or three rounds and you're back where you started, it's worth getting the whole picture evaluated before starting another.

Frequent Asked Questions about SIBO

Why does SIBO keep coming back after antibiotics?

Quick Answer: Antibiotics clear the bacteria and leave the underlying cause in place. If that cause persists, the overgrowth tends to return.

Full Answer: In one study, 44% of successfully treated patients had a positive breath test again within nine months [5]. The common drivers I find are a stalled migrating motor complex, long-term acid suppression, slow transit from thyroid or other conditions, and methane that was treated like hydrogen.

What are the symptoms of SIBO?

Quick Answer: Bloating that builds through the day, gas, abdominal pain, and diarrhea or constipation are the most common.

Full Answer: Hydrogen-dominant SIBO tends to come with looser stools in my practice. Methane-dominant overgrowth is associated with constipation [3]. More advanced cases can affect absorption of fat and vitamin B12 [1]. These symptoms overlap with IBS and celiac disease, so testing matters.

How accurate is the SIBO breath test?

Quick Answer: It's useful and imperfect. Results depend on preparation and on how fast your gut moves.

Full Answer: Rapid transit can produce a false positive, and slow stomach emptying can produce a false negative [3]. I interpret every breath test alongside your history and risk factors, and I repeat a test when the preparation was poor or the result doesn't fit the story.

What is the difference between SIBO and IMO?

Quick Answer: SIBO is bacterial overgrowth in the small intestine. IMO is an overgrowth of methane-producing archaea, which can also live in the colon.

Full Answer: IMO stands for intestinal methanogen overgrowth. It's diagnosed when breath methane reaches 10 parts per million or more [1], and it's associated with constipation [3]. Treatment differs, which is why knowing the gas matters before choosing a therapy.

Are herbal antimicrobials as effective as rifaximin for SIBO?

Quick Answer: One study found similar results. The evidence base for rifaximin is much larger.

Full Answer: In a Johns Hopkins study, 46% of patients on herbal therapy and 34% on rifaximin had a normal follow-up breath test, with no statistically significant difference [9]. In my practice I use both, and I choose based on the gas type, your history, and your preference.

What should you eat if you have SIBO?

Quick Answer: Diet can ease symptoms, and it doesn't clear the overgrowth. Meal timing matters as much as food choice.

Full Answer: I often use a low FODMAP diet as a short-term tool during treatment. I also ask patients to space meals four to five hours apart so the gut's cleaning wave can run. Long-term restriction is rarely the goal.

Can a PPI cause SIBO?

Quick Answer: PPI use is associated with a higher risk of SIBO. Stomach acid is one of the gut's defenses against swallowed bacteria.

Full Answer: A meta-analysis found about 1.7 times the odds of SIBO in people taking proton pump inhibitors [6]. Some people need these medications. If you take one long term and have recurrent SIBO, it's worth reviewing with your prescriber. Please don't stop it on your own.

Find Out Why Your SIBO Keeps Coming Back

Dr. Wool's Gut Repair Plan starts with extended visits, specialty testing conventional workups rarely include, and a treatment plan built around root cause rather than symptom management.

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References

1. Pimentel M, Saad RJ, Long MD, Rao SSC. ACG clinical guideline: small intestinal bacterial overgrowth. Am J Gastroenterol. 2020;115(2):165-178. doi:10.14309/ajg.0000000000000501. https://doi.org/10.14309/ajg.0000000000000501

2. Chen B, Kim JJ, Zhang Y, Du L, Dai N. Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis. J Gastroenterol. 2018;53(7):807-818. doi:10.1007/s00535-018-1476-9. https://doi.org/10.1007/s00535-018-1476-9

3. Lim J, Rezaie A. Pros and cons of breath testing for small intestinal bacterial overgrowth and intestinal methanogen overgrowth. Gastroenterol Hepatol (N Y). 2023;19(3):140-146. https://www.gastroenterologyandhepatology.net/archives/march-2023/pros-and-cons-of-breath-testing-for-small-intestinal-bacterial-overgrowth-and-intestinal-methanogen-overgrowth/

4. Gatta L, Scarpignato C, McCallum RW, et al. Systematic review with meta-analysis: rifaximin is effective and safe for the treatment of small intestine bacterial overgrowth. Aliment Pharmacol Ther. 2017;45(5):604-616. doi:10.1111/apt.13928. https://pmc.ncbi.nlm.nih.gov/articles/PMC5299503/

5. Lauritano EC, Gabrielli M, Scarpellini E, et al. Small intestinal bacterial overgrowth recurrence after antibiotic therapy. Am J Gastroenterol. 2008;103(8):2031-2035. doi:10.1111/j.1572-0241.2008.02030.x. https://pubmed.ncbi.nlm.nih.gov/18802998/

6. Su T, Lai S, Lee A, He X, Chen S. Meta-analysis: proton pump inhibitors moderately increase the risk of small intestinal bacterial overgrowth. J Gastroenterol. 2018;53(1):27-36. doi:10.1007/s00535-017-1371-9. https://pubmed.ncbi.nlm.nih.gov/28770351/

7. Low K, Hwang L, Hua J, Zhu A, Morales W, Pimentel M. A combination of rifaximin and neomycin is most effective in treating irritable bowel syndrome patients with methane on lactulose breath test. J Clin Gastroenterol. 2010;44(8):547-550. doi:10.1097/MCG.0b013e3181c64c90. https://pubmed.ncbi.nlm.nih.gov/19996983/

8. Lauritano EC, Bilotta AL, Gabrielli M, et al. Association between hypothyroidism and small intestinal bacterial overgrowth. J Clin Endocrinol Metab. 2007;92(11):4180-4184. doi:10.1210/jc.2007-0606. https://pubmed.ncbi.nlm.nih.gov/17698907/

9. Chedid V, Dhalla S, Clarke JO, et al. Herbal therapy is equivalent to rifaximin for the treatment of small intestinal bacterial overgrowth. Glob Adv Health Med. 2014;3(3):16-24. doi:10.7453/gahmj.2014.019. https://pmc.ncbi.nlm.nih.gov/articles/PMC4030608/

10. Pimentel M, Constantino T, Kong Y, Bajwa M, Rezaei A, Park S. A 14-day elemental diet is highly effective in normalizing the lactulose breath test. Dig Dis Sci. 2004;49(1):73-77. doi:10.1023/B:DDAS.0000011605.43979.e1. https://pubmed.ncbi.nlm.nih.gov/14992438/

11. Pimentel M, Morales W, Lezcano S, Sun-Chuan D, Low K, Yang J. Low-dose nocturnal tegaserod or erythromycin delays symptom recurrence after treatment of irritable bowel syndrome based on presumed bacterial overgrowth. Gastroenterol Hepatol (N Y). 2009;5(6):435-442. https://pmc.ncbi.nlm.nih.gov/articles/PMC2886395/

Disclaimer

The information provided on this page is for educational purposes only and is not intended as medical advice, diagnosis, or treatment. Dr. Dan Wool nor his affiliates do not make claims about the effectiveness of supplements, peptides, hormones or other therapies outside of the contexts supported by cited clinical evidence and regulatory approval. Always consult a qualified healthcare provider before starting, changing, or stopping any medical or wellness program.