Is your IBS really SIBO?
You've been told you have IBS. You've cut out foods, tried the diets, and you're still bloated, uncomfortable and unsure what to eat. For many people with an IBS diagnosis, small intestinal bacterial overgrowth (SIBO) is part of what's going on, and it can be tested for.
Sound familiar?
Do you plan your day around where the nearest loo is?
Do your jeans fit in the morning but not by evening?
Has your list of foods you feel safe eating got shorter and shorter?
What is SIBO?
Most of your gut bacteria live in the large intestine, where they belong. The small intestine is where you digest and absorb your food, and it is meant to hold very few bacteria.
SIBO happens when too many bacteria, or the wrong types, build up in the small intestine. They ferment food before your body has had the chance to absorb it, producing gas. That gas stretches the gut, changes how quickly things move through it, and can irritate the gut lining.
How SIBO can feel
Symptoms vary a lot from person to person, and many people are told they have IBS. Research suggests a large share of people with an IBS diagnosis may have SIBO underneath it.
In the gut
- Bloating and a swollen tummy, often worse as the day goes on
- Abdominal pain or cramping
- Diarrhoea, constipation, or both
- Excess wind and burping
- Nausea and feeling full quickly
- Reflux or heartburn
Beyond the gut
- Tiredness that seems out of proportion
- Brain fog and poor concentration
- Multiple food intolerances, with more foods causing problems over time
- Signs of inflammation around the body, such as aching joints and puffiness
- Skin flare-ups, such as rosacea or hives
- Low mood or anxiety
- Low iron or B12
SIBO or something else?
Bloating is a symptom, not a diagnosis. These conditions can feel very similar, but each leaves its own clues and has its own test.
| Possible cause | Typical clues | How it's checked |
|---|---|---|
| SIBO | Bloating soon after most meals, building through the day. Reacting to many different foods. Often started after a gut infection. | Breath test for hydrogen and methane gases |
| Lactose intolerance | Symptoms within a few hours of milk, soft cheese, ice cream or yoghurt. Fine without dairy. | Lactose breath test, or a supervised trial without dairy |
| Fructose malabsorption | Symptoms after fruit, fruit juice, honey or sweeteners such as agave. | Fructose breath test |
| Coeliac disease | Symptoms linked to gluten, often with tiredness, low iron or weight loss. Can run in families. | Blood test, which must be taken while you are still eating gluten. Genetic testing can be done at any time, and can rule coeliac disease out but not confirm it. |
| Constipation | Hard or infrequent stools, with bloating that eases after a bowel movement. | History and symptoms. It can also be a sign of methane overgrowth. |
| Low stomach acid or digestive enzymes | Heaviness or fullness after protein-rich or fatty meals, pale or floating stools. | History and stool testing |
These conditions can also overlap. That's why I start with a detailed history and test rather than guess. Finding the root cause is vital, because it gives you the best chance of stopping symptoms coming back.
What can cause SIBO?
Your gut has several built-in defences that keep bacteria out of the small intestine. SIBO develops when one or more of them stops working well, so finding the reason is a big part of the work.
A gut infection or food poisoning
One of the most common triggers. Some infections can damage the nerves that keep the gut moving, sometimes months before symptoms settle in.
A slower-moving gut
Between meals, a "cleaning wave" sweeps bacteria down the gut. Constant snacking, stress, poor sleep and some health conditions can weaken it.
Medications
Long-term acid-reducing tablets, opioid painkillers and other medicines that slow the gut can all play a part.
Previous abdominal surgery
Operations such as an appendectomy, caesarean or hysterectomy can leave adhesions that change how the gut moves.
Low stomach acid or enzymes
Stomach acid, bile and pancreatic enzymes all help keep bacterial numbers in check.
Other health conditions
An underactive thyroid, diabetes, coeliac disease, Crohn's disease and connective tissue conditions such as EDS are all linked with SIBO.
What working with me looks like
Every plan is personal, but most clients follow a similar path. Most people work with me for three to six months. Some types of SIBO take longer to settle.
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£125
Initial consultation and plan
A detailed look at your history, symptoms, diet, medications and what may have triggered things, so we know what to test and why. You then receive a personalised, phased plan covering what you eat and when, support for your gut lining and how your gut moves, and clearing any overgrowth.
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£179
SIBO breath test (if needed)
An at-home breath test that measures the gases produced in your gut over a few hours. I interpret the results with you and explain what they mean.
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£65 each
Follow-ups and maintenance
Regular check-ins to adjust the plan and a retest where it is useful. In one study, SIBO returned within nine months for 44% of people whose overgrowth had cleared, so once it has cleared we map out a maintenance plan together, including how to widen your diet again and keep SIBO from returning.
What if it's not SIBO?
If your breath test is clear, or your history points elsewhere, there are other tests that can help us find the cause of your symptoms.
Common questions
Is SIBO the same as IBS?
No. IBS is a name for a pattern of symptoms. SIBO is one possible cause of those symptoms, and it can be tested for. Many people with an IBS diagnosis turn out to have SIBO.
Can I get tested on the NHS?
Breath testing is available through some NHS gastroenterology departments, usually by referral, and waiting times can be long. A private test gives results more quickly.
Will a low-FODMAP diet fix it?
A low-FODMAP diet can ease symptoms by giving the bacteria less to ferment, but it doesn't clear the overgrowth. It is also not meant to be followed long term.
Do I need to prepare for the breath test?
Yes. The test needs a simple diet the day before and an overnight fast, and some medications and supplements need pausing beforehand. I'll guide you through it step by step.
Wondering if SIBO could be behind your symptoms?
Book a free discovery call. We'll talk through what's going on and whether testing makes sense for you.
BOOK A FREE DISCOVERY CALLEmail pip@pipflemingnutrition.com
Phone +44 7958 986892
Pip (Philippa) Fleming · Nutritional Therapist, Dip ION, mBANT, CNHC registered