IBS & SIBO NATUROPATH · MAROOCHYDORE, SUNSHINE COAST & ONLINE
IBS vs SIBO
What's the Difference?
Why the symptoms overlap, what actually distinguishes them and when SIBO breath testing may help clarify the next step
You have been told it is IBS, but you may still feel as though no one has explained why your digestion has become so unpredictable.
Perhaps your abdomen is relatively comfortable when you wake, then becomes increasingly swollen after meals. Foods you once ate without thinking now seem to trigger bloating, pain, diarrhoea or constipation. You may have tried cutting out gluten, dairy or FODMAPs, only to find that the list of foods you trust keeps getting smaller.
If probiotics made you worse, a restricted diet helped only temporarily or your symptoms returned after treatment, it is understandable to wonder whether something has been missed.
This is often where the question arises: Could this be SIBO rather than IBS?
The honest answer is that symptoms alone usually cannot tell us.
IBS and small intestinal bacterial overgrowth can both involve bloating, abdominal pain and altered bowel habits. They are not the same condition, but they can overlap, and SIBO is not automatically the hidden “root cause” of every IBS presentation.
The useful question is whether SIBO is clinically plausible, whether testing would add meaningful information and what else needs to be considered before deciding on treatment.
You do not need to work this out before booking.
RECOGNISING THE OVERLAP
When “it’s IBS” has not felt like a complete answer
An IBS diagnosis may be clinically appropriate and still leave you with questions.
You may have been reassured that your blood tests, scan or colonoscopy were normal, yet your symptoms continue to affect what you eat, what you wear and whether you feel comfortable leaving home.
You may recognise patterns such as:
Bloating or visible distension that becomes more pronounced through the day
Abdominal pain, cramping or pressure that changes after opening your bowels
Constipation, diarrhoea or movement between the two
Urgency, straining or a persistent feeling of incomplete emptying
Feeling unusually full after an ordinary meal
Excessive wind, belching or digestive gurgling
Foods seeming increasingly difficult to tolerate
Temporary improvement during a low FODMAP or restricted diet
Symptoms returning when foods are reintroduced
Probiotics, prebiotic fibres or fermented foods making bloating worse
Previous SIBO treatment helping briefly, or not helping at all
These experiences matter, but none of them reliably separates IBS from SIBO.
Even the commonly described pattern of waking flatter and becoming more distended after eating is not exclusive to bacterial overgrowth. It can also occur with constipation, altered gut movement, fermentation, visceral sensitivity and changes in how the abdominal wall responds to pressure.
Feeling recognised is important. Being given an assumed diagnosis from a symptom list is not enough.
UNDERSTANDING IBS
IBS is more than “nothing showed up on your tests”
Irritable bowel syndrome is a disorder of gut–brain interaction characterised by recurrent abdominal pain and a change in bowel habits.
Depending on the predominant bowel pattern, it may be described as:
IBS with constipation — IBS-C
IBS with diarrhoea — IBS-D
IBS with mixed bowel habits — IBS-M
Unclassified IBS — IBS-U
IBS does not mean symptoms are imagined, caused solely by stress or unimportant because routine investigations are normal.
Changes in intestinal sensitivity, bowel movement, fermentation, immune signalling, the gut–brain relationship and the way the body responds to food or stress may all contribute. The relative importance of these factors differs from one person to another.
IBS can often be diagnosed positively from the symptom pattern after appropriate assessment, rather than being treated as a meaningless label given only when every possible test is negative.
However, other conditions can resemble IBS. The history, age of onset, family history, alarm features and previous investigations help determine whether further medical assessment is needed.
UNDERSTANDING SIBO AND IMO
SIBO describes a different clinical problem
Small intestinal bacterial overgrowth describes an abnormal number or composition of bacteria within the small intestine that contributes to gastrointestinal symptoms.
The small intestine normally contains microorganisms, but its environment differs from the colon. When the mechanisms that regulate microbial numbers and movement are disrupted, fermentation within the small intestine may contribute to gas, bloating, discomfort and altered bowel habits.
In more significant presentations, digestion and nutrient absorption may also be affected. This is not present in everyone with suspected or diagnosed SIBO.
Methane detected on breath testing is more accurately described as intestinal methanogen overgrowth, or IMO, rather than methane SIBO. Methane is produced by archaea, not bacteria, and the overgrowth may involve the small intestine or colon. It is particularly relevant when constipation and slow transit are prominent.
SIBO or IMO may be more plausible when the symptom pattern occurs alongside factors such as altered intestinal movement, significant constipation, previous gastrointestinal surgery, structural changes, certain medical conditions or a history of gastroenteritis.
IBS and SIBO are different, but they are not opposites
What it describes
IBS
A disorder of gut–brain interaction involving recurrent abdominal pain and altered bowel habits
A clinical condition involving abnormal microbial numbers or composition in the small intestine; methane overgrowth is termed IMO
SIBO/IMO
Common symptoms
IBS
Abdominal pain, bloating, constipation, diarrhoea, urgency or incomplete evacuation
Bloating, distension, gas, abdominal discomfort, urgency, incomplete evacuation, diarrhoea, constipation, or both
SIBO/IMO
How it is assessed
Clinical history, recognised symptom criteria and appropriate investigation for alternative conditions or alarm feature
IBS
Clinical history and risk factors, with breath testing or less commonly small-bowel sampling used to support assessment
SIBO/IMO
What symptoms can prove
IBS
Symptoms may form a recognisable IBS pattern
SIBO/IMO
Symptoms cannot confirm SIBO or identify the gas pattern
What a normal scan
or colonoscopy means
IBS
Normal structural tests can be consistent with IBS
SIBO/IMO
These tests do not generally confirm or exclude SIBO
Can they overlap?
IBS
Yes. A person with IBS may also have a positive breath test
Yes. A positive result does not mean every symptom is caused by SIBO
SIBO/IMO
Treatment focus
Depends on the bowel pattern and may include diet, bowel function, gut–brain therapies, and symptom-specific care
IBS
May involve medical or practitioner-directed treatment, bowel and motility support, nutrition and attention to contributing factors
SIBO/IMO
WHY THE CONFUSION PERSISTS
The same symptom can arise through different mechanisms
Bloating is the clearest example.
With SIBO, microbial fermentation may contribute to gas production and abdominal symptoms.
With IBS, the intestine may be more sensitive to normal or only modest amounts of gas and stretching. Constipation, delayed transit, pelvic-floor dysfunction, meal size, carbohydrate fermentation and changes in the coordination of the diaphragm and abdominal wall may also contribute to bloating or visible distension.
This means the severity of bloating does not reliably tell us how much gas is present, or whether SIBO is the cause. Food reactions overlap too.
Fermentable carbohydrates can aggravate symptoms in IBS and SIBO. Feeling better on a low FODMAP diet therefore does not diagnose bacterial overgrowth. It shows that changing fermentation reduced symptoms, but not why the sensitivity developed.
The same applies to probiotics. Feeling worse after a probiotic may be useful information about the product, dose and current digestive tolerance, but it does not function as a home test for SIBO.
A symptom response can guide the assessment without proving the diagnosis.
When SIBO may be worth considering
SIBO or IMO may deserve closer consideration when:
Bloating, distension or altered bowel habits remain persistent despite appropriate IBS care
Constipation, hard stools or incomplete emptying suggest markedly slowed transit and a possible methane-associated pattern
Symptoms began after gastroenteritis or another relevant gastrointestinal illness
There is a history of abdominal surgery, structural change or a medical condition that may affect intestinal movement
Previous antibiotic or targeted SIBO treatment produced a clear but temporary response
A previous SIBO diagnosis was made without testing and the response to treatment was unclear
The result would genuinely change the next treatment decision
No single item confirms SIBO. The overall pattern determines how persuasive the possibility is.
TESTING
When SIBO breath testing may add useful information
Hydrogen and methane breath testing is the most accessible non-invasive method used to investigate suspected SIBO and IMO.
After a preparation diet and fasting period, a measured carbohydrate solution, usually glucose or lactulose, is consumed. Breath samples are then collected over several hours to measure gases produced through microbial fermentation.
Breath testing can be helpful, but it is not a perfect yes-or-no test.
The result can be affected by the substrate used, intestinal transit time, preparation, sample collection and the interpretation criteria applied. A rapid movement of lactulose into the colon may be difficult to distinguish from small-intestinal fermentation, while glucose may be absorbed before reaching overgrowth farther along the small intestine.
A positive breath test can support a diagnosis when the result fits the clinical picture. It does not prove that SIBO explains every symptom.
A negative result does not mean the symptoms are insignificant. It may redirect attention toward IBS, constipation, food malabsorption, pelvic-floor dysfunction, another motility issue or a different gastrointestinal condition.
Comprehensive stool testing does not diagnose SIBO because stool primarily reflects the large-intestinal environment.
When testing may not be the best next step
Breath testing is not automatically the most useful first step when:
The symptoms are new, severe or accompanied by features requiring medical assessment
Significant constipation or incomplete evacuation has not yet been properly assessed
The preparation instructions cannot be followed accurately
Recent antibiotics, laxatives or other treatments may compromise the result
The result would not change the proposed treatment
Testing is being used to justify an increasingly restricted diet
Several previous tests and treatment rounds have not produced a coherent pattern
In these situations, ordering another test can create more data without creating more clarity.
Sometimes the better first decision is to improve bowel regularity, review medical investigations, stabilise food intake or reconsider whether the original diagnosis still fits.
MY APPROACH
I do not assume persistent IBS symptoms mean SIBO
SIBO is sometimes presented as the overlooked explanation behind almost every case of bloating or IBS.
That is too simplistic.
My role is to determine what the history actually supports, which questions remain unanswered and whether breath testing is likely to improve the treatment decision.
01 — Clarify the pattern
We organise when the symptoms began, how pain relates to bowel movements, whether constipation or diarrhoea predominates, how symptoms change after meals and what is affecting daily life most.
02 — Review what has already been done
Previous pathology, scans, endoscopy, breath testing, medication, diets, supplements and treatment responses are considered together.
I am particularly interested in what clearly improved, what worsened and whether any benefit lasted.
03 — Decide what genuinely needs clarification
The next step may involve SIBO breath testing, medical investigation, constipation or motility support, a targeted dietary strategy or treatment of an established IBS pattern.
Not everyone needs functional testing, and not every digestive symptom needs to be treated at once.
04 — Build a focused starting plan
Recommendations are matched to the strongest current priority, with a timeframe, measurable markers and a clear review point.
If the response does not support the working explanation, the diagnosis and plan should be reconsidered rather than expanded indefinitely.
What treatment may involve
The treatment direction depends on which features are actually present.
For someone with IBS and constipation, the first priority may be improving stool consistency, ease and completeness rather than immediately ordering a breath test.
For someone with diarrhoea, weight loss or possible malabsorption, medical investigation may need to come first.
For someone with a clinically plausible SIBO or IMO pattern, breath testing may help decide whether targeted treatment is reasonable.
For someone who has already completed several SIBO protocols without lasting improvement, repeating the same “kill phase” may be a poor next step. It may be more useful to reconsider bowel transit, dietary restriction, the accuracy of the original diagnosis and whether the remaining symptoms still represent bacterial overgrowth.
Depending on the assessment, care may involve:
Nutrition and meal-pattern changes
Constipation and bowel-function support
A structured, time-limited low FODMAP strategy where appropriate
Gradual food reintroduction and dietary expansion
Practitioner-prescribed herbal medicine or nutritional supplements
Correction of identified nutritional deficiencies
SIBO breath testing when the result is likely to influence management
You do not need to know whether it is IBS or SIBO before booking
You may already have an IBS diagnosis and wonder whether it explains enough.
You may be considering your first SIBO test, or you may have completed treatment before and still be dealing with bloating, food reactions or unpredictable bowel habits.
Your initial consultation is used to organise the full pattern, review what has already been investigated and determine which next step is most likely to provide useful information.
That may be SIBO breath testing. It may be a focused IBS approach, medical follow-up, bowel support or a different digestive pathway.
The aim is not to give you the most complicated explanation.
It is to identify the strongest priority, make the next decision deliberate and stop you cycling through increasingly restrictive or aggressive protocols without a clear reason.
Consultations are available in Maroochydore and at Kunara Marketplace in Forest Glen on the Sunshine Coast, and online throughout Australia.
Frequently asked questions
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Not automatically.
SIBO may contribute to symptoms in some people with IBS, but IBS is heterogeneous and can involve several interacting mechanisms. Presenting SIBO as the hidden cause of every IBS case overstates the evidence and can lead to unnecessary testing, antimicrobial treatment and food restriction.
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You generally cannot distinguish them from bloating alone.
The timing, bowel pattern, medical history, risk factors and response to previous treatment may raise or lower suspicion, but no symptom pattern confirms SIBO.
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No.
A low FODMAP diet can reduce fermentation-related symptoms in people with IBS as well as SIBO. Improvement shows that changing fermentable carbohydrate intake affected symptoms; it does not establish the underlying diagnosis.
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No.
Some people experience more gas or bloating from particular probiotic strains, doses or added prebiotic ingredients. This response may guide product choice, but it does not diagnose SIBO.
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No.
Testing is most useful when the history makes SIBO or IMO clinically plausible and the result would influence treatment. An IBS diagnosis or bloating alone is not enough reason to test everyone.
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Yes. I require an initial consultation before ordering a SIBO breath test.
This allows me to assess whether testing is appropriate, identify anything requiring medical investigation and ensure that the result is likely to inform your care.