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If you’re struggling with bloating, constipation, diarrhoea, gas, or unexplained digestive discomfort, Small Intestinal Bacterial Overgrowth (SIBO) could be the hidden cause. SIBO occurs when bacteria, whether beneficial or harmful, accumulate in the small intestine where they don’t belong, leading to a wide range of gut-related and systemic symptoms.
The good news? There’s a simple, non-invasive way to find out the cause. The SIBO Test from Smart Nutrition is a trusted at-home SIBO breath test designed to detect this imbalance. Convenient, fast, and fully supported by a UK-based accredited lab, it’s the ideal first step to understanding and addressing your symptoms.
SIBO stands for Small Intestinal Bacterial Overgrowth, a condition where excess bacteria is present in the small intestine, disrupting normal digestion and absorption. Unlike the large intestine, where bacteria naturally thrive, the small intestine should contain relatively low levels of bacteria.
When this delicate balance is disturbed, these bacteria begin to ferment carbohydrates in your food prematurely, producing gases like hydrogen and methane. This fermentation can lead to a variety of uncomfortable symptoms, including bloating, gas, abdominal pain, and irregular bowel movements.
SIBO has been linked to more than just digestive discomfort. Research suggests it may play a role in conditions such as:
Because SIBO can mimic or worsen many chronic health conditions, identifying it through accurate breath testing is a crucial step in personalised treatment planning.
One of the most common underlying causes is reduced motility, a slowing or disruption of the natural movement of food through the digestive tract.
Think of your gut like a flowing stream: when food moves efficiently, bacteria are swept along and kept in balance. But if that stream becomes stagnant, like a still pond, it creates the perfect environment for bacteria to multiply inappropriately.
There are two main causes of slow mobility in the gut:
Before collecting your SIBO breath samples, follow a 24-hour preparation diet (48 hours if constipated), then fast overnight – water is allowed. Full instructions will be included with your test kit.
For your prep diet, please choose from:
Example Meal Plan
| Breakfast | Snack | Lunch | Snack | Dinner |
| Scrambled eggs | Chicken broth | Chicken and white rice seasoned with salt and pepper | Chicken broth | Fish and white rice seasoned with salt and pepper |
| Drinks | ||||
| Water is allowed throughout the day as needed. | ||||
Preparation
Some medications can affect test results, so please speak to your GP before making any changes. Smart Nutrition, along with our partner laboratory, do not recommend stopping any medication without your doctor’s guidance.
One week before testing
One day before testing
On the day of the test
Don’t let unexplained symptoms go undiagnosed. With fast results, expert insights, and convenient at-home testing, the Smart Nutrition SIBO Test is your first step towards better gut health.
Order now and take control of your digestive wellbeing.
Most common SIBO symptoms:
Other related digestive SIBO symptoms:
Less well known SIBO symptoms:
Research shows the main cause of small intestinal bacterial overgrowth (SIBO) is a reduction or slowing of motility (the movement of food) through the gut. Imagine your digestive system flowing like a stream, then think of a stagnant pond where bacteria can easily flourish and grow in large unwanted amounts opposed to a clean, free-flowing stream, which keeps bacteria levels as they should be.
1. The cleansing sweeping action, ‘Migrating Motor Complex’ MMC in the gut stops working properly. The MMC makes cleansing, sweeping-like motions between meals that “clean” the small intestine. This should move undigested food and excess bacteria towards the large intestine. When the MMC is faulty, undigested food becomes food for the bacteria, causing or exacerbating SIBO. The major cause of malfunctioning MMC is food poisoning.
2. Structural changes which affect the motility of the gut can also cause SIBO. Some diseases, medical conditions and procedures can cause these structural changes. For example, scarring after operations, inflammatory bowel disease, diverticulosis, blind loops, radiation damage, stricture, fistulas, intestinal pseudo-obstruction and adhesions resulting from surgery are all known to impact or cause SIBO.
Our at-home SIBO test measures levels of Hydrogen and Methane in the breath.
After drinking a sugary (fermentable) solution, elevated levels of hydrogen and methane in the breath indicate an overgrowth of bacteria, ie SIBO.
You will need to collect 10 breath samples over 3 hours, which ensures more accurate results compared to the usual 7 samples taken over 2.5 hours.
This is important as it adds value when interpreting and understanding results. And adds value when comparing a repeat test after any SIBO treatment plans.
The SIBO Test is suitable for;
Adults: suitable for all ages.
Children: Children need to be competent in blowing into a balloon, and we need to know the weight of your child so that we can advise about the correct amount of the solution to drink. Please speak to us and consult your medical professional to discuss a suitable dosage of the solution prior to completing this test.
Your SIBO test results will be ready in 5 working days.
No, the cost of the Smart SIBO Test includes testing only.
We don’t offer a one-size-fits-all treatment plan because SIBO is complex and often chronic, requiring a tailored approach. Treatment depends on the type of SIBO (hydrogen, methane, or hydrogen sulfide), and other factors like fungal overgrowth (SIFO) or co-existing gut imbalances.
Instead, we provide referral options to experienced Functional Medicine practitioners and nutritional therapists who can create a bespoke treatment plan based on your results and individual needs. You’ll receive their details with your test results if you wish to seek further support.
I have lactose intolerance and want to do the SIBO test. Will this be a problem?
The solution used to carry out the SIBO test is made up of lactose, galactose or epilactose however, it is not broken down from this complex when in the body and does not enter the bloodstream, but it would be sensible for patients who are allergic to avoid it.
Do I need to follow any special dietary requirements for the SIBO test?
Yes, you will need to follow a special low-fermentation diet for 1 day before the test, or if constipated, for 2 days. The instructions include full details about the diet, including meal ideas.
I have just finished a course of antibiotics. Can I still do the SIBO test?
You need a break of two weeks after antibiotics before you can do the SIBO test.
I have just finished a course on natural plant-based antimicrobials. Can I still do the SIBO test?
You need a break of two weeks after a course of natural antimicrobials before you can do the SIBO test.
I take probiotics. Can I still do the SIBO test?
You need a break of two weeks after stopping probiotics before you can do the Smart SIBO test.
Can I take laxatives the night before the SIBO test?
Unfortunately not, laxatives would interfere with the test results. If your laxatives are prescribed, please discuss with your doctor whether stopping them for 1 day is OK for you. You can take laxatives if needed on the day of the test, after you have finished taking your breath samples.
Do I need to stop any supplements before doing the SIBO test?
You need to stop probiotics for 2 weeks before the test. Digestive aids such as digestive enzymes and betaine HCL (stomach acid) should be stopped the day before the test.
Do I need to stop taking any medication before I do the SIBO test?
Do not stop any medication without your doctor’s approval. PPIs can be continued, but take them after the test on the day of collection (if approved).
Can I drink water the night before the SIBO test when fasting?
Yes, drinking water is allowed while fasting.
I have just had a colonoscopy. Can I still do the SIBO test?
You must wait at least 1 month after a colonoscopy before doing the SIBO test.
I have just had some Barium studies. Can I still do the SIBO test?
You must wait at least 1 month after having Barium studies before doing the Smart SIBO test.
Preparation for the test
You will be sent full instructions with your SIBO test kit. To do the test you will need to follow a prep diet for 1 day, or if constipated 2 days before the SIBO test and then you will need to fast overnight before doing the test. Water is allowed whilst fasting. Your instructions include details about which foods you can eat and provide a meal plan as well.
On the day of the test
In the morning you will take a control breath sample and then drink the solution provided with the test kit. You then collect a breath sample every 20 minutes for the next 3 hours. After the last sample has been collected you can then eat and drink as normal.
Should I remove the grey rubber around the needle of the breath collecting kit?
No, Please don’t remove it. It helps to produce a good seal around the vial.
There is a hole in the blue breath collection bag. Should I tape it up?
The hole is there on purpose. Please don’t tape it up. It helps to get the correct breath sample.
Have you any tips re taking the breath sample?
Please have a look at the video that explains how to take the sample but feedback I have been given is that stand in front of a mirror may help you to see what you are doing.
Should I be able to see my breath in the test tube?
You generally won’t be able to see your breath go into the test tube but you might see some condensation.
Returning your samples
Samples need to arrive back at the lab within 7 days of completing the samples.
The vials can be posted by airmail should you be outside the UK.
All sample reports are for representational and educational purposes only. Biomarkers, references ranges, results, and all other data may differ from actual reports. All data included in no way represents an actual patient. Any comparisons of results to actual patients is completely incidental.
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Please do not return samples to the laboratories that may arrive after Wednesday 27th March and up to and including Monday 2nd April.
The laboratories are closed from the 28th March – 2nd April for the Easter Holiday.