SIBO (small intestinal bacterial overgrowth) is a real condition in which bacteria multiply in the upper gut in numbers that normally don't live there, causing bloating, diarrhea and malabsorption. But over the past two decades the name has become a ready-made explanation for almost any gas or bloating, often diagnosed with a breath test that was never designed for the job. This article separates the genuine disease from "the diagnosis that explains everything," and explains who actually needs testing.
The short version: the more symptoms a diagnosis explains, the less it tells you about their cause. The right question isn't "Do I have SIBO?" but "Do I have a reason that would make SIBO likely in the first place?"
🔬 What is SIBO, exactly?
The small intestine isn't sterile, but it is sparsely populated compared with the colon. Stomach acid kills much of what we swallow, and steady waves of gut movement keep sweeping contents downstream, so bacteria never get the chance to settle. That's why the American College of Gastroenterology (ACG) 2020 guideline states that healthy people typically carry fewer than 1,000 colony-forming units per millilitre (10³ CFU/mL) of small-bowel fluid, and that a count at or above that level in an aspirate from the duodenum or jejunum is generally considered diagnostic of overgrowth.
When one of those two defences fails, acid or motion, or when surgery changes the shape of the gut itself, bacteria get their opening. They start fermenting food before it is absorbed, producing gas, and they can consume vitamin B12 and interfere with fat absorption. Mayo Clinic lists the complications as poor absorption of fats, proteins and carbohydrates, deficiencies of the fat-soluble vitamins (A, D, E, K) and B12, and weakened bones over time.
This is "classic" SIBO: a disease with an identifiable cause and a measurable footprint in your bloodwork and on the scale. It is also one of the reasons a person can run low on B12 even when their diet contains plenty of it.
🧩 How did SIBO become the diagnosis that explains everything?
Originally, SIBO was a relatively uncommon diagnosis, looked for in a thin patient with diarrhea and malabsorption after, say, stomach surgery. Then something shifted. Professor Eamonn Quigley, chief of gastroenterology at Houston Methodist, described the shift in a 2025 review with a telling title: "From Malabsorption to Misinterpretation."
According to Quigley, SIBO "is being invoked to explain almost every gastrointestinal symptom": bloating, diarrhea and constipation, especially in people with irritable bowel syndrome (IBS). And many of those diagnoses rest on tests "that were never designed, or validated, for that purpose."
A year earlier, in 2024, a Mayo Clinic team led by Dr. Purna Kashyap published an updated appraisal of what they call "the SIBO hypothesis." They concluded that the SIBO-IBS link remains unproven and has led to "injudicious use of antibiotics," and they called for "a more targeted approach" that looks for SIBO in people at genuine risk rather than testing everyone with gut symptoms.
Why does this happen? Common symptoms are always looking for a name, and a name that promises one cause and one cure is more comforting than "a functional disorder" that doesn't show up on any lab report. But a diagnosis that fits everyone distinguishes no one.
🌬️ Why isn't a SIBO breath test enough on its own?
The idea behind the breath test is simple. You drink a sugar solution (lactulose or glucose). If bacteria are living in the small intestine, they ferment it early and release hydrogen or methane, which shows up in your breath. Under the ACG guideline, a test is positive if hydrogen rises by 20 parts per million or more above baseline within 90 minutes, or if methane reaches 10 parts per million or more.
The problem is a hidden assumption: that the sugar is still in the small intestine during those 90 minutes. Lactulose isn't absorbed, so it travels on to the colon, which is full of bacteria anyway. Houston Methodist's summary of Quigley's review notes it can arrive there in about 40 to 70 minutes in some healthy people, and the Mayo team writes that transit time to the colon is "remarkably short in many healthy people" and in people with IBS. When that happens, an early hydrogen rise comes from a normal colon, not from overgrowth. That's why the Mayo authors describe the lactulose test as "primarily a measure of intestinal transit" with "very low sensitivity and specificity," one that can yield false positives in "a very high proportion of individuals."
The glucose test is more accurate because glucose is absorbed early, but it still produces false positives, especially after gut surgery, and the Mayo team calls its performance "unacceptable for routine clinical use in patients with IBS."
Change the tool, change the number
The clearest illustration comes from a 2009 meta-analysis by Ford and colleagues in Clinical Gastroenterology and Hepatology, pooling 12 studies and 1,921 people with IBS. The share who "had SIBO" depended on the test used:
Lactulose breath test: 54%
Glucose breath test: 31%
Jejunal aspirate culture (the more direct reference): 4%
Same kind of patient, and more than a thirteen-fold gap between the highest and lowest figure (our arithmetic from the study's own numbers). The authors concluded that the role of SIBO testing in IBS "remains unclear." The lesson: a reported SIBO rate often measures the instrument more than the disease.
Even direct sampling isn't the final word
In a 2019 study in Nature Communications, a Mayo Clinic team (Saffouri and colleagues) found that SIBO diagnosed by duodenal aspirate culture reflected an overgrowth of a particular group of bacteria, but "does not correspond with patient symptoms." What did track with symptoms was a change in the composition of small-bowel bacteria, not their count. In other words, "how many bacteria are there?" may not be the right question at all.
That is why recent reviews argue medicine needs to move beyond breath tests to direct molecular profiling of the small-intestinal microbiome. We aren't there yet.
🎯 Who actually needs SIBO testing?
Here the question shifts from "What are your symptoms?" to "What in your medical history makes SIBO plausible?" Mayo Clinic and Cleveland Clinic describe the classic picture clearly. The genuine risk factors either knock out one of the two defences or change the shape of the gut:
Previous abdominal surgery: bariatric or ulcer surgery, partial stomach removal, or adhesions from earlier operations.
Slow gut movement: gastroparesis, scleroderma, long-standing diabetes affecting the gut's nerves, or an underactive thyroid.
Structural change: pouches in the small-bowel wall, a fistula, Crohn's-related narrowing, or radiation therapy to the abdomen.
Other associated conditions: celiac disease, cirrhosis, chronic kidney failure, weakened immunity and older age.
The ACG recommendations follow the same logic. They suggest breath testing in people with symptoms and previous luminal abdominal surgery, in suspected motility disorders, and also in IBS. What stands out is that all six of the guideline's recommendations are conditional, not strong: five rest on "very low" quality evidence and the sixth, on antibiotics, on "low" quality evidence. That isn't a flaw in the guideline; it's honesty about the limits of what we know.
In practical terms: if you have chronic bloating but none of those risk factors, and no weight loss, anaemia or night-time diarrhea, SIBO probably isn't the first question to ask. The more common causes of bloating, and how the FODMAP framework works, are a better starting point. If you've also wondered about dairy, our guide to lactose intolerance explains a different hydrogen breath test, one built for a narrower question.
💊 Acid-reducing medicines and SIBO: should you worry?
Proton pump inhibitors (PPIs) such as omeprazole and pantoprazole reduce stomach acid, weakening one of the two defences, which is why Cleveland Clinic lists them among the risk factors. Yet the ACG guideline explicitly suggests against breath testing in people taking PPIs who have no symptoms. A risk factor on its own is not a disease worth hunting for.
What does the Saudi data say?
We looked for a Saudi study measuring SIBO itself and found no published dataset we could rely on. The closest we found, published in the Saudi Journal of Gastroenterology in 2011, was actually conducted in Pakistan. So we won't invent a local number. What does exist is data on the commonest risk factor, acid-reducing medicine, and it points in two different directions:
Jeddah, 2021 (King Abdulaziz University Hospital): in a retrospective review of 1,135 medical-ward patients, 62.5% received a PPI, but an indication was documented for only 13%, and about 48% were discharged on one. The authors acknowledge that many may have had a valid reason that simply wasn't recorded.
Qatif, 2024 (Qatif Central Hospital): in the records of 41,084 outpatients aged 40 or over, 31% were prescribed a PPI. But the authors' main concern ran the other way: 70% of patients with stomach-related conditions and 68% of those on anti-inflammatory painkillers were not prescribed one, even though many had a reason to be.
Setting the two studies side by side is our reading, not the authors'. What it suggests is that the problem isn't "too many" or "too few" acid reducers, but a missing, documented reason in both directions. The takeaway for you: don't stop an acid-reducing medicine out of fear of a SIBO you read about online. At your next appointment, ask your doctor: why am I taking this, and for how long?
💉 Treatment: what antibiotics do, and what they don't
When SIBO is real, antibiotics are the cornerstone of treatment according to ACG and Cleveland Clinic. The American Gastroenterological Association's (AGA) 2020 clinical practice update reports that a single 7–10 day course improved symptoms in roughly 45% to 90% of patients, and stresses that the goal is symptom relief, not eradicating bacteria.
Three facts make antibiotics a tool to use with care rather than casually:
First: treatment is largely empiric, chosen without knowing exactly which bacteria are responsible.
Second: symptoms often return months later, especially when the underlying cause (surgery, slow motility) remains. Cleveland Clinic calls antibiotics "a short-term SIBO treatment, but not a long-term solution," and there is no clear evidence supporting any particular retreatment strategy.
Third: even when someone with IBS improves on the antibiotic rifaximin, Quigley believes it probably works by reducing fermentation in the colon, not the small bowel. Feeling better doesn't prove the diagnosis was right.
That is why the Mayo team warns against antibiotic use driven by unreliable breath tests: every course carries a cost to the whole gut microbiome and to antibiotic resistance.
🥗 Where does food fit into SIBO?
Bacteria feed on whatever fermentable carbohydrate reaches them. The ACG guideline says "the dominant theme in diet manipulation for SIBO is the reduction of fermentable products," while noting that the data are extrapolated from IBS trials rather than SIBO directly. Cleveland Clinic notes that some providers prescribe a short-term elimination diet that restricts carbohydrates, such as a low-FODMAP diet, and that a low-carbohydrate eating plan may help, though the studies are "inconclusive."
In Saffouri's small pilot study, switching people from a high-fibre diet to a low-fibre, high-simple-sugar diet triggered gut symptoms, reduced small-bowel microbial diversity and increased the permeability of the intestinal lining. It's a preliminary finding from very few participants, but it fits a simple idea: simple sugar doesn't pass through the gut neutrally.
As for probiotics, the ACG guideline states there is a lack of consistent data to recommend specific probiotics for SIBO. Don't let a supplement stand in for a diagnosis.
One practical caution: if you're trialling a low-FODMAP diet under professional supervision, remember that sugar alcohols are polyols, and they don't all ferment the same way. Read the label and ask your dietitian how much suits you.
⚠️ When to see a doctor promptly, and who should be careful
Mayo Clinic recommends a full medical evaluation, especially if you've had abdominal surgery, for any of the following, and immediate care for severe abdominal pain:
- Persistent diarrhea that isn't improving.
- Rapid, unintentional weight loss.
- Abdominal pain lasting more than a few days.
- Unusually oily, floating or foul-smelling stools, which can signal poor fat absorption.
- Marked fatigue, anaemia or tingling in the hands and feet, which can be signs of B12 deficiency.
- Blood in the stool or a lasting change in bowel habits after age 45. These must never be put down to SIBO before other causes are ruled out; see our guide to colorectal cancer screening.
Extra caution applies to people who have had bariatric or stomach surgery, people with long-standing diabetes and delayed stomach emptying, and people with celiac disease whose symptoms persist despite a strict gluten-free diet. These are the patients the test was built for.
This article is for education only and is no substitute for medical advice. Don't start an antibiotic, a supplement or a prolonged elimination diet, or stop a prescribed medicine, without talking to your doctor.
🍞 Where does Bakery 8 stand in all this?
Let's be clear: no bread treats SIBO, including ours. If you have genuine overgrowth, its treatment is with your doctor and its cause is in your medical history, not your shopping basket. If you don't have it, switching bread won't create a diagnosis that wasn't there.
We should also declare an interest: we sell low-carb products, and an article that says "cut the sugar" suits us commercially. That's why we've stuck to what the guideline actually says. Reducing fermentable carbohydrate is the main dietary direction, but the evidence is indirect, and some "sugar-free" products on the market contain sugar alcohols that may not suit someone on a low-FODMAP plan.
What we offer is simpler than treatment: an everyday alternative to white bread and simple-sugar sweets for people who have decided, with their doctor or dietitian, to cut back on carbohydrates. That might be our almond-flour keto bread, gluten-free with no added sugar, crackers as a snack instead of sweet biscuits, or keto granola for a breakfast that doesn't lean on refined grains. Check each product's ingredients on its page and decide based on what suits your own gut.
❓ SIBO: frequently asked questions
Does a positive breath test mean I have SIBO?
Not necessarily. A lactulose test can be falsely positive if the sugar reaches the colon early, which is common in healthy people. The glucose test is more accurate but not definitive. A result should be read alongside your risk factors, symptoms and blood tests, never on its own.
What's the difference between SIBO and IBS?
SIBO has an identifiable cause, such as surgery or slow gut movement, and can lead to malabsorption and vitamin deficiencies. IBS is a functional disorder diagnosed when no clear structural cause is found. The two can coexist, but recent reviews say the popular link between them remains an unproven hypothesis.
Do acid-reducing medicines cause SIBO?
Lowering stomach acid weakens one line of defence, so PPIs count as a risk factor. But the ACG guideline suggests against testing people who take them without symptoms. Don't stop the medicine yourself; ask your doctor why it was prescribed, for how long, and whether you still need it.
Does a low-carb diet cure SIBO?
There is no evidence that it cures it. The ACG guideline says reducing fermentable carbohydrate is the main dietary direction, but its data come from IBS studies, and Cleveland Clinic calls the evidence inconclusive. The main treatment for confirmed SIBO is an antibiotic under medical supervision.
Do probiotics help with SIBO?
According to the ACG's 2020 guideline, there is a lack of consistent data to recommend specific probiotics for SIBO. Buying expensive supplements on the strength of an unreliable breath test may mean paying for a diagnosis that was never established. Discuss it with your doctor before you start.
✅ The bottom line
Small intestinal bacterial overgrowth is a real disease, usually in people with a clear reason for it: surgery, slow motility or a change in the gut's structure. But it has become a label handed to almost any bloating, based on a test that measures transit speed more than bacteria, and the reported rate swings from 4% to 54% depending on the tool. Before asking "Do I have SIBO?", ask "Do I have a reason for it?" And before any antibiotic or supplement, see your doctor.
When you and a professional decide to cut back on simple sugar and refined flour, you'll find low-carb, gluten-free options at Bakery 8 in Riyadh, Saudi Arabia, to make that decision easier.
📚 References
- Pimentel M, Saad RJ, Long MD, Rao SSC. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. American Journal of Gastroenterology. 2020;115(2):165–178.
- Quigley EMM, et al. AGA Clinical Practice Update on Small Intestinal Bacterial Overgrowth: Expert Review. Gastroenterology. 2020 (summarised by MDedge, September 2020).
- Ford AC, Spiegel BMR, Talley NJ, Moayyedi P. Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome: Systematic Review and Meta-analysis. Clinical Gastroenterology and Hepatology. 2009;7(12):1279–1286.
- Kashyap P, et al. An updated appraisal of the SIBO hypothesis and the limits of breath testing. Neurogastroenterology and Motility. 2024;36:e14817 (summarised by Mayo Clinic, October 2024).
- Saffouri GB, Shields-Cutler RR, Chen J, et al. Small intestinal microbial dysbiosis underlies symptoms associated with functional gastrointestinal disorders. Nature Communications. 2019;10:2012.
- Quigley EMM. Small Intestinal Bacterial Overgrowth: From Malabsorption to Misinterpretation. Minerva Gastroenterology. 2025 (summarised by Houston Methodist, November 2025).
- Cleveland Clinic. SIBO (Small Intestinal Bacterial Overgrowth). Last updated 2024.
- Mayo Clinic. Small intestinal bacterial overgrowth (SIBO): Symptoms and causes. 2024.
- Al-Dosari BS, Binafeef BM, Alsolami SA. Prescribing pattern of proton pump inhibitors among patients admitted to medical ward at King Abdulaziz University Hospital, Jeddah. Saudi Medical Journal. 2021;42(12):1313–1319.
- Alqurain AA, Alomar MF, et al. Pattern of Prescribing Proton Pump Inhibitors: Evaluating Appropriateness and Factors Contributing to Their Adverse Effect Reaction Risk. Journal of Clinical Medicine. 2024;13(20):6187.
Related keywords: SIBO, small intestinal bacterial overgrowth, hydrogen breath test, bloating and gas, IBS, acid reflux medicines, malabsorption, vitamin B12 deficiency.