Understanding SIBO: Testing, Nutrition Support and Long-Term Gut Care
- Ola Krawczyk, Clinical Nutritionist
- Sep 17, 2025
- 7 min read
Updated: 3 days ago
Written by Ola Krawczyk, Clinical Nutritionist
ATMS Accredited Member | SIBO-Certified Nutritionist | Microba Certified Nutritionist
Published: 17 September 2025 | Last reviewed: 5 September 2026
Small intestinal bacterial overgrowth, commonly known as SIBO, occurs when excessive numbers or an altered balance of bacteria are present in the small intestine and contribute to gastrointestinal symptoms.
Common symptoms include bloating, abdominal distension, excessive gas, abdominal discomfort, diarrhoea or constipation. In more significant cases, SIBO may contribute to poor nutrient absorption or deficiencies.
Managing SIBO usually involves more than following a restrictive diet. Appropriate testing, medical treatment, personalised nutrition and investigation of possible underlying causes may all be important.
Ola’s clinical perspective:“SIBO nutrition support should not be based on one fixed list of foods. I consider the person’s symptoms, bowel habits, test results, nutritional status, medical history and food tolerance so the plan remains practical and nutritionally balanced.” — Ola Krawczyk, Clinical Nutritionist and SIBO-Certified Practitioner
What are the symptoms of SIBO?
SIBO symptoms may include:
Bloating, particularly after eating
Visible abdominal distension
Excessive gas or belching
Abdominal discomfort
Diarrhoea
Constipation
Alternating bowel habits
Nausea
Feeling uncomfortably full after meals
Food-related digestive symptoms
These symptoms are not exclusive to SIBO. IBS, constipation, coeliac disease, food intolerances and other digestive conditions can produce similar symptoms.
Symptoms alone cannot confirm SIBO.
Seek medical advice if you experience blood in your stool, unexplained weight loss, persistent vomiting, fever, iron-deficiency anaemia, severe abdominal pain or diarrhoea that wakes you during the night.
How does SIBO breath testing work in Australia?
A hydrogen and methane breath test is commonly used to investigate suspected SIBO or intestinal methanogen overgrowth.
Before the test, you will receive preparation instructions. These may include temporarily avoiding certain medications or supplements, following a specific preparation diet and fasting overnight.
Do not stop prescribed medication without consulting your doctor.
During the test:
You provide an initial breath sample.
You drink a measured glucose or lactulose solution.
You collect additional breath samples at scheduled intervals.
The laboratory measures gases produced during fermentation.
Microorganisms generate gases when they ferment the test solution. Some of these gases enter the bloodstream, travel to the lungs and are released in your breath.
In Australia, a GP, gastroenterologist or another suitably qualified healthcare professional may recommend or arrange testing. Some laboratories also allow people to order an at-home test directly.
At-home hydrogen and methane breath tests can be ordered through SIBO Test Australia.
What do the different gas patterns mean?
Hydrogen
An early increase in hydrogen may support a diagnosis of hydrogen-predominant SIBO when interpreted according to the laboratory’s criteria.
Hydrogen elevation is often associated with diarrhoea, bloating or abdominal discomfort, but symptoms differ between individuals.
Methane
Methane is produced by archaea rather than bacteria. A methane-positive result is therefore more accurately called intestinal methanogen overgrowth, or IMO.
Higher methane production is commonly associated with constipation and slower intestinal transit. Methanogens may be present in the small or large intestine.
Hydrogen sulphide
Hydrogen-sulphide testing is a newer development and is not included in every SIBO breath test available in Australia.
Hydrogen-sulphide patterns are being investigated in relation to diarrhoea and urgency. However, symptoms such as foul-smelling gas cannot diagnose this pattern.
Always check which gases the selected laboratory measures. A standard hydrogen and methane test should not be described as a three-gas test.
Is breath testing completely accurate?
No gastrointestinal breath test is perfect.
A 2020 systematic review found that glucose testing had pooled sensitivity of approximately 54.5%, while lactulose testing had pooled sensitivity of approximately 42%. Specificity was higher, but results varied considerably between studies.
This means a positive or negative result should be considered alongside:
Symptoms
Bowel patterns
Medical and surgical history
Medications
Risk factors
Test preparation
Other relevant investigations
Glucose or lactulose: which test is better?
Both have advantages and limitations.
Glucose is absorbed earlier in the small intestine. It may be more specific for overgrowth in the upper small intestine but could miss overgrowth located further down.
Lactulose is not absorbed and travels through the intestinal tract. It may provide information across a longer testing period, but rapid transit can make small-intestinal fermentation difficult to distinguish from normal fermentation in the colon.
The choice should reflect your symptoms, history and the clinical question being investigated.
For a detailed comparison, read SIBO Breath Testing vs Gut Microbiome Testing.
If you would like this mapped to your own test results and symptoms, that is what SIBO nutrition support is for.
What happens after a positive SIBO test?
A positive result should be reviewed alongside the wider clinical picture. It does not automatically explain why bacterial overgrowth developed.
Important considerations include:
Whether constipation or slow motility is present
Previous gastrointestinal surgery
Diabetes, thyroid or neurological conditions
Coeliac disease or other digestive conditions
Current medications
Previous gastrointestinal infection
Possible nutrient deficiencies
Medical treatment should be managed by a GP, gastroenterologist or another appropriately qualified medical practitioner. Treatment may include prescribed antibiotics selected for the person’s presentation.
Herbal antimicrobials are sometimes promoted for SIBO, but evidence is more limited, products vary and interactions or adverse effects are possible. They should not be assumed to be suitable or safer for everyone.
Nutrition support can work alongside medical care to help manage symptoms and maintain an adequate diet.
What should you eat during SIBO treatment?
There is no single SIBO diet suitable for everyone.
During active symptoms or medical treatment, nutrition support may focus on:
Maintaining adequate protein and energy
Choosing carbohydrates according to tolerance
Adjusting portions of highly fermentable foods
Including suitable cooked vegetables
Supporting regular bowel movements
Drinking enough fluid
Using smaller meals when fullness is significant
Avoiding unnecessary long-term food restriction
Some people benefit from temporarily reducing foods that significantly worsen fermentation-related symptoms. Others can continue eating a much broader diet.
The aim is to reduce discomfort without creating nutritional deficiencies or fear around food.
Is a low-FODMAP diet necessary for SIBO?
Not always.
FODMAPs are fermentable carbohydrates that may increase gas and fluid in the intestine. Temporarily reducing selected FODMAPs can help some people manage bloating, pain or altered bowel habits.
However, the low-FODMAP diet was developed primarily as a symptom-management strategy for IBS. It is not a stand-alone treatment for SIBO and should not remain highly restrictive long term.
Monash University recommends progressing from restriction to structured reintroduction and personalisation. Read the Monash three-step approach
Depending on the person, the most appropriate option may be:
Reducing only the main trigger foods
A short structured low-FODMAP trial
A modified lower-fermentation approach
Focusing primarily on constipation
Maintaining the usual diet during medical treatment
What should you do during a SIBO flare?
During a temporary increase in symptoms, return to simple meals you already know you tolerate.
A comfortable meal may include:
Eggs, fish, chicken, tofu or another tolerated protein
Rice, potato, quinoa or another tolerated carbohydrate
Cooked vegetables in manageable portions
Suitable fruit
Olive oil or another tolerated fat
Water and appropriate fluids
Avoid fasting, juice-only cleanses or removing multiple food groups without a clear plan.
A flare does not necessarily mean SIBO has returned. Constipation, a large meal, stress, illness, hormonal changes or increased fermentable foods may cause similar symptoms.
How do you rebuild your diet after SIBO treatment?
Rebuilding after treatment is an important part of long-term care.
The goal is not to remain on a restrictive “SIBO diet.” It is to gradually return to a varied and nutritionally balanced way of eating.
Reintroduce foods gradually
Introduce one food or food group at a time in a manageable portion. This makes symptoms easier to assess.
A small increase in gas does not always mean SIBO has returned. The digestive system may need time to adjust to increased fibre and fermentation.
Increase fibre carefully
Fibre supports bowel regularity and the large-intestinal microbiome, but suddenly increasing it may worsen bloating.
The most suitable type and amount depend on your bowel habits, symptoms and tolerance.
Rebuild plant variety
Where tolerated, gradually include a wider range of:
Vegetables
Fruit
Legumes
Wholegrains
Nuts
Seeds
Herbs and spices
Plant variety should be increased at a comfortable pace rather than according to a rigid target.
Support bowel regularity
Constipation and slow transit may contribute to recurring symptoms. Long-term support may include suitable fibre, adequate fluid, regular movement and medical management when necessary.
Review nutritional status
Depending on your history and symptoms, your doctor may consider:
Full blood count
Iron studies
Vitamin B12
Folate
Vitamin D
Other relevant investigations
Deficiencies should be identified and addressed appropriately rather than assumed from symptoms.
Why does SIBO come back?
SIBO may return when treatment reduces bacterial overgrowth but the factor that allowed it to develop remains.
Possible contributors include:
Impaired intestinal motility
Chronic constipation
Previous gastrointestinal surgery
Structural changes
An impaired or removed ileocecal valve
Diabetes-related motility changes
Hypothyroidism that is not adequately managed
Gastroparesis
Coeliac disease
Certain medications
Learn more in What Causes SIBO?.
Frequently asked questions
Can food cure SIBO?
No particular food or diet has been shown to cure SIBO. Nutrition can help manage symptoms and support nutritional adequacy alongside medical care.
Should I avoid fibre?
Not automatically. Some fibres may aggravate symptoms, while others can support bowel regularity. Fibre should be personalised.
Should I take probiotics after treatment?
Probiotics are not automatically required. Responses vary, and some people experience increased bloating. The product and individual circumstances matter.
Does recurring bloating mean SIBO has returned?
Not necessarily. IBS, constipation, food intolerance and hormonal or dietary changes may cause similar symptoms. Reassessment may be needed before repeating treatment.
Can a stool microbiome test diagnose SIBO?
No. Stool testing primarily reflects the large-intestinal microbiome and cannot confirm or exclude bacterial overgrowth in the small intestine.
The bottom line
SIBO management is not a single diet or universal supplement protocol.
A considered approach may include appropriate testing, medical treatment, investigation of underlying contributors, personalised nutrition and gradual rebuilding of fibre and food variety.
The long-term goal is to help you move towards a broader, sustainable diet—not remain afraid of food after treatment.
Personalised SIBO nutrition support
If you have confirmed SIBO, are considering testing or feel unsure about what to eat after treatment, I can help you review your symptoms, breath-test results, diet, bowel patterns and nutrition goals.
I provide evidence-informed SIBO nutrition support alongside appropriate medical care, with online consultations available across Australia.
This article is for educational purposes only and does not replace medical diagnosis or treatment. Discuss SIBO diagnosis and medical treatment with your GP, gastroenterologist or another appropriately qualified medical practitioner.
About the author
Ola Krawczyk is a Polish-Australian Clinical Nutritionist, accredited ATMS member, SIBO-Certified Nutritionist and Microba Certified Nutritionist specialising in SIBO, digestive health, microbiome interpretation, thyroid health and perimenopause nutrition.
Ola provides personalised, evidence-informed online nutrition consultations across Australia through Clinical Nutrition by Ola.
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