What Is A SIBO Test?

If you’re looking for information on SIBO testing, you’ve probably heard that small intestinal bacterial overgrowth (SIBO) might be contributing to your symptoms, but you’re not sure of the next steps.

There are a few different kinds of SIBO tests, but they’re not all available to everybody. A lot depends on where you live, and whether you go through the NHS or a private practitioner.

We’ll take you through all the types of SIBO tests and how they work, and explain how to do a SIBO test at home. And, most importantly, we’ll share the next steps on what to do if you get a positive result.

At IBS Clinics, our industry-leading SIBO test forms part of our range of gut microbiome home testing kits.

What is SIBO? 

Small intestinal bacterial overgrowth (SIBO) happens when bacteria move from your large intestine (where they should be) to your small intestine (where they shouldn’t be).

Research has found that up to 15% of people have SIBO, and many experts believe it to be the leading cause of IBS. However, because the above symptoms are common in many other conditions, to find out if you have SIBO, you need to take a test.

Depending on the type of SIBO test, it will measure either the levels of bacteria in your small intestine or the gases they produce. 

What are the symptoms of SIBO? 

In your small intestine, bacteria ferment the carbohydrates you eat and release gas as a by-product. They also eat some of the nutrients from your food. Sometimes, when there are too many bacteria there, you get uncomfortable symptoms, including:

• Bloating
• Abdominal pain
• Belching
• Flatulence
• Nausea
• Fatigue
• Brain fog
• Fatty stools

What is a SIBO test? 

A SIBO test shows the levels of bacteria you have living in your small intestine. Unlike your large intestine, which is home to trillions of microbes, your small intestine should house a small, select population of bacteria, yeasts and other microbes.

When too many bacteria start to live and multiply there, that’s SIBO.

If you want to find out if you have SIBO, there’s only one way to find out for sure. You need to take a test.

By far the most common type of SIBO test is the breath test. We explain all three types later, but for now, let’s just look at the breath test.

You can take a SIBO breath test at home, or in a hospital or clinic. 

Mainstream medicine only recently started to accept that SIBO was a common condition, so you couldn’t get a SIBO test through the NHS unless you had a very specific history and set of symptoms.

IBS symptoms are now inextricably linked to SIBO: up to 85% of IBS sufferers have been found to have SIBO. As the evidence has grown, more NHS trusts have begun to carry out SIBO tests, so your GP may refer you to a gastroenterologist, who can test you for SIBO in a hospital. 

However, depending on the area you live in, or what your GP believes about SIBO, a SIBO test might not be an option for you.

Whether you get tested through the NHS or a private clinic, you’ll almost certainly get a breath test. Most people who test themselves at home also use a breath test.

Every SIBO breath test uses a carbohydrate solution which you’ll drink at the beginning of the test. There are three types of solution: lactulose, glucose, and fructose. Most health practitioners prefer to use lactulose.

SIBO breath tests can measure two types of gases: methane and hydrogen. The test can last for two to three hours, depending on the clinician that carries it out or the test provider. The majority of SIBO breath tests now measure both gases and last for three hours. Some NHS trusts and gastroenterologists may still use a two-hour test and only test for hydrogen, however. 

Some also use a glucose solution instead of lactulose which has been shown to produce more false negative results. At IBS Clinics, we believe it’s important to test for methane and hydrogen gases, as methane has been shown to produce constipation and other symptoms in several studies. 

At IBS Clinics we use a three-hour SIBO test, which measures both hydrogen and methane gases. We recommend you use lactulose for the solution. You can choose to use glucose or fructose if you prefer, though.

You’ll receive the test kit within two to three days of your request, and you’ll need to follow a special diet for the day before the test. 

You’ll get your results within 7 to 10 days.

How does a SIBO test work? 

The SIBO breath test works by measuring the gases that bacteria ferment when they consume the carbohydrates in the solution you drink. When they do that, they release hydrogen and methane gas as a by-product. 

Eighty percent of this gas passes through your intestines, but the other 20% is absorbed into your blood and travels round to your lungs—where you breathe it out. When we know the levels of those gases in your breath, we have a good idea of how many bacteria are present.

It’s important to point out that we aren’t measuring the actual bacteria, but the gases they produce. That gives us an indication of both the type and volume of bacteria in your small intestine. In the past, most SIBO breath tests only measured hydrogen, but today most measure both hydrogen and methane, as excess levels of both gases have been shown to produce symptoms. 

Types of SIBO test 

SIBO testing is available on the NHS, but not all trusts provide it. If you do get a test through the NHS, it’s likely to be a breath test.

There are two other ways to test for SIBO in the UK: by aspiration, or with a urine test. However both methods have drawbacks and health professionals rarely use them.

Here’s the lowdown on all three.

Small intestine aspiration and quantitative culture

This involves taking a sample of bacteria from your small intestine and culturing it. It’s considered the gold standard of SIBO testing because it can tell exactly what’s growing in your small intestine. But it has issues:

1. Bacteria from your large intestine can contaminate the sample.
2. Some bacteria won’t survive outside of your gut, so won’t show up on the culture results.
3. It’s very expensive.
4. A sample is only taken from one area of your small intestine, which doesn’t help the diagnosis if the bacteria are overgrown in another area.

Organic acids

This is an easy, non-invasive test that analyses your urine for evidence of microbial metabolites (the substances that microbes produce when they eat). There are specific biomarkers that, if raised, can indicate SIBO.

This method is much easier than the small intestine aspiration and quantitative culture, but again, results can easily be skewed. Also, there’s not much evidence that backs up its validity.

SIBO breath test

This is the simplest and most reliable SIBO test. A decade ago, you’d probably have visited a clinic to carry out the test, but today most SIBO tests happen at home.

After a day of a special diet and a 12-hour fast, you begin your test by giving a ‘baseline’ sample, before you drink a sugary solution: lactulose, glucose or fructose. After that, you collect samples of your breath by breathing into a tube every 20 minutes for 2.5 hours. When you’ve filled all the tubes, you send them off to the lab, where technicians will analyse your breath to measure the levels of gases present.

Where can I get a SIBO test? 

Many private medical labs offer SIBO breath tests, or you can order a SIBO breath test online. There are a lot websites today selling SIBO tests, so it’s important to make sure you check that it’s a reliable company first. At IBS Clinics we use an industry-leading breath test from Genova Diagnostics.

SIBO test NHS 

If your NHS trust doesn’t test for SIBO, your GP can’t refer you for one. If you live in an area where the NHS doesn’t test for SIBO, you can get a SIBO test privately, either through us at IBS Clinics or another provider.

Some NHS tests may only measure hydrogen. The test should also last for three hours to get the most accurate result. Unfortunately, some hospitals and clinics only run two-hour tests.

At IBS Clinics, we use three-hour SIBO tests that analyse both hydrogen and methane. Find out more about our SIBO test.

SIBO test online 

If you’ve ordered a SIBO breath test through IBS Clinics, the test kit will be delivered straight to your door, usually within three days.

You’ll need to follow a special diet for the day before the test, and then fast on the day of the test until it’s over, so you might find it easiest to do on a weekend. That way, you can set aside a day for the restricted diet and then a morning to do the test. 

Make sure you follow all the instructions in the kit in the lead up to the test to make sure your test results are as accurate as possible. Every test provider may give slightly different instructions.

For the test we use at IBS Clinics, first give a baseline breath sample using one of the tubes in the kit provided. Then drink the sugary solution, and wait 30 minutes. After 30 minutes, give another breath sample in a second tube. Repeat this process every 20 minutes for a total of 2.5 hours. 

At the end, you’ll have a batch of breath-filled tubes to send off to the lab. When it’s over, you can eat normally again while you wait for the results. You should get your results back within 7 to 10 days.

How much should I pay for a SIBO test? 

If your GP suspects you may have SIBO, they might refer you to a gastroenterologist for a test. 

The number of NHS hospitals offering SIBO breath testing is growing. You may find that you can get both the test and treatment through your GP, which means it will cost you only the price of the prescription.

Your NHS trust may not offer SIBO testing, or only offer a hydrogen test. If you have methane SIBO and you use a hydrogen only test, you’ll get a false negative result.

Because of the uncertainty, possible waiting time and the need to attend a hospital appointment, a lot of people find it easier to pay for a private SIBO test.

Most online SIBO breath tests cost between £120 to £200. But before you pay for one, you need to find out whether the provider will give you a glucose, lactulose or fructose solution, and if they test for both hydrogen and methane. 

Our SIBO tests at IBS Clinics cost between £139 and £165. This includes all test materials and results.

How is a SIBO test done? 

To take a hydrogen breath test, you’ll need to eat a special diet the day before, then fast on the day of the test. To start, you’ll need to give a baseline breath sample in the first bag. Then you’ll drink a sugary solution (usually lactulose) and breathe into the rest of the bags supplied with the test kit every 20 minutes 2.5 hours afterwards.

When you’re finished, you’ll send the bags off to a lab where technicians will analyse the levels of hydrogen and methane in your breath. The result reflects the levels of bacteria in your small intestine.

How to test for SIBO at home 

The process is easy if you prepare properly and read the instructions in the test kit thoroughly. All the information you need is in the instructions, but if you’d like to know more now,, we’ve outlined the process here.

Step one
The day before you take the test, you’ll need to eat a low-fibre diet. That means meat, eggs, and refined carbohydrates like white bread and rice. You’ll need to fast for 8-12 hours before making your first breath sample, so your natural overnight fast while you sleep works well. You can collect your first sample in the morning by breathing into the first glass tube. This is your baseline sample, before you drink the solution. It will be used to compare the rest of your samples to.

Step two
Once you’ve collected your first sample, you’ll need to drink the sugary solution provided in your test kit. Simply mix it with 200ml water, and drink. Your gut bacteria soon start to eat it, and give off gases. 

Twenty minutes after drinking the solution, you can take your next breath sample. Continue to make the rest of the samples at every interval for 2.5 hours, until you have 10 samples in total. Make sure you label each one as you take it, so the technicians at the lab can display your results correctly.

Step three
When you’ve made all your samples, you simply need to post them back to the lab using the return envelope provided. You’ll get your results  in 7 to 10 days after the lab receives your samples.

How soon will I get my test results? 

We can’t speak for other providers, but our SIBO test results usually take 7 to 10 days from the day you send off your test samples.

How do I interpret my SIBO test results? 

As more labs began to test for SIBO, it became obvious that there was a lack of standardisation in both taking the test and giving results. To clear things up, a group of experts met in 2017 to agree on some guidelines, which became known as ‘The North American Consensus’.

In the consensus, the experts agreed on the following:

Positive for hydrogen-predominant SIBO
If there is a rise in hydrogen of 20 p.p.m. (parts per million) from baseline within 90 minutes, this is considered positive for hydrogen-predominant SIBO.

Positive for intestinal methanogen overgrowth
A level of at least 10 p.p.m of methane at any time is considered positive for intestinal methanogen overgrowth.

There’s also a third type of overgrowth, made up of hydrogen sulphide producing bacteria. There’s currently no way to test for hydrogen-sulphide predominant SIBO. Practitioners look for low levels of both hydrogen and methane to deduce if hydrogen sulphide is likely to be present.

What is the treatment for SIBO? 

Whether you’re positive for hydrogen or methane, or you have a suspected hydrogen sulphide overgrowth, you know you have too many bacteria producing gases in your small intestine.

The next step is to get rid of these excess bacteria, but it’s important to also improve the environment of your whole digestive system too. This means following a tailored diet designed to starve the bacteria of their preferred food supply and taking antimicrobial supplements to reduce their numbers, as a minimum. We also recommend other measures to improve your overall gut health and address the reasons you got SIBO in the first place.

Everyone’s treatment is different, but here’s an idea of what your plan might include:

A low carbohydrate diet
Carbohydrates feed bacteria. Some types of carbohydrates feed bacteria more than others, and there are a range of different diets that cut down their food supply in various ways. You’ll usually follow one for six to eight weeks to reduce the overgrowth.

Examples include the low-FODMAP diet, the Specific Carbohydrate Diet and the Bi-Phasic Diet. Most practitioners recommend that you personalise whatever diet you choose: it’s not usually necessary for you to follow it religiously. These diets aren’t supposed to be followed for a long period of time, so you’ll need to reintroduce foods after a set period of time.

Antimicrobials
While a doctor will prescribe antibiotics to get rid of bacterial overgrowth, studies have found that natural antimicrobials can be equally effective.

There are specific antimicrobials that have been found to work on all three types of overgrowth: hydrogen, methane or hydrogen sulphide. They include oil of oregano, berberine, neem, garlic and others.

You should only take antimicrobials for a specific period of time. Practitioners usually recommend anything from six to 10 weeks. 

Prebiotics and probiotics
Prebiotics are substances that feed microbes. Strangely, some have been found to help SIBO.

For example, a type of prebiotic fibre called partially hydrolysed guar gum has been proven to help alleviate methane-predominant SIBO. There’s also evidence that some probiotics can tackle SIBO.

However, many probiotics can worsen SIBO. Every individual has a different reaction to each probiotic, but studies suggest that the species Lactobacillus casei, Bifidobacterium breve and Bifidobacterium bifidum are more helpful than harmful. Saccharomyces boulardii—which is actually a yeast—is a favourite of many practitioners.

Find the root cause
Research shows that SIBO has a high rate of recurrence—around 80%—because there are reasons that SIBO happens in the first place that people don’t always address.

The human body naturally prevents SIBO from happening through a variety of ways:

• Hydrochloric acid in your stomach kills almost all bacteria on contact, if there’s enough of it.
• Gut motility pushes food through your small intestine quickly enough to prevent excessive fermentation by bacteria.
• Pancreatic juices and bile also stop bacteria from fermenting and multiplying.
• Your ileo-cecal valve—the door between your small intestine and large intestine—stops material from the large intestine from backing up into the small intestine.
• Antibodies help to destroy too many bacteria in the wrong place.

If you have SIBO, one or more of these mechanisms isn’t working properly. If you want to dig deeply into your gut health, working with a health practitioner who can uncover and address imbalances in your gut and the rest of your body is a great place to start.

What if your SIBO test result is negative? 

If you don’t have SIBO, your symptoms must be happening as a result of something else.

SIBO symptoms, like diarrhoea, bloating and constipation can happen for a huge variety of reasons, but addressing your gut health is a good thing to do regardless of whether or not you have SIBO. Some people decide to follow a SIBO protocol like the one above anyway, and find that their symptoms get better.

After a negative SIBO result, we recommend you take one of the following next steps:

• Take the test again: Almost all tests have a small chance of coming back with a false negative. Some people decide to take a second test to check they get the same results again.
• Think about what else could be going on and test for that. Dysbiosis in your large intestine can produce very similar symptoms to SIBO. You may be low on bacterial diversity or have an overgrowth of certain types or strains, for example. Our Gut Health Tests look at parasites, viruses, yeasts, leaky gut, antibiotic resistance and a whole host of other markers to shine a light on the health of your gut and beyond.
• Speak to a qualified practitioner who will look at your full health history and your past and present symptoms to build a plan of what to do next. 

Conclusion 

There are a few ways you can test for SIBO, but breath testing is the simplest, most reliable and least expensive. If you prepare properly, it’s an accurate way to measure the bacterial growth in your small intestine.

At IBS Clinics, our SIBO breath test will tell you if you have hydrogen-predominant SIBO or methane-predominant SIBO. A skilled practitioner will also be able to deduce if you could have hydrogen-sulphide-predominant SIBO.

Test results are a powerful tool, but to make the most of them, we recommend you talk to a qualified practitioner who can explain them and give you a treatment plan to tackle your symptoms, whether you have SIBO or not.

Author: Alexandra Falconer

Alexandra Falconer MA (Dist) DipCNM mBANT is a Nutritionist and Registered Nutritional Therapist. After graduating from Brighton’s College of Naturopathic Medicine in 2018, she set up her nutrition practice specialising in gut health, IBS, IBD and related conditions.

Before becoming a nutritionist, Alex was a journalist and copywriter. Now, she combines her two great loves—words and natural medicine—to help bring vibrant health to everyone who needs it.

Reviewed by: Tracey Randell