What Does A SIBO Test Show? Diagnosis, Accuracy and Results

A SIBO hydrogen breath test shows whether or not you have too many bacteria living in your small intestine. Unlike your large intestine, which is supposed to be teeming with trillions of microbes, your small intestine should be home to a small, select population of bacteria and other microscopic organisms.

When too many set up shop there, you have small intestinal bacterial overgrowth: SIBO.

Could taking a SIBO test help you? If you want to know why you should take a SIBO test, and what the results could mean for you, read on.

Quick Answers

  • A SIBO breath test is the most effective and common way to test for SIBO
  • You can ask your GP to refer you for a SIBO test, but it’s not always easy and may take a while
  • The test should show the levels of hydrogen and methane in your small intestine, but some tests only show hydrogen
  • Hydrogen levels reflect the numbers of bacteria in your small intestine
  • Methane levels reflect the numbers of archaea in your small intestine
  • SIBO breath tests are accurate but not perfect
  • It’s important to work with an experienced practitioner who will use the test results as a tool to build a picture of your general gut health

What are the symptoms of SIBO?

The most common symptoms of SIBO are:

  • Diarrhoea
  • Constipation
  • Bloating
  • Food intolerances (especially to certain carbohydrates)

For all you need to know about SIBO symptoms, check out our blog SIBO symptoms: what they mean and what to do next.

Could your symptoms be SIBO?

View our at home SIBO test

What does a breath test diagnose?

Breath tests are used to diagnose many conditions. SIBO is just one of them. Others include:

  • Lactose intolerance
  • Fructose intolerance
  • H. pylori

The SIBO breath test is the industry gold standard. That means that most experts agree it’s the best way to test for SIBO.

A doctor can also test for SIBO using something called an aspirate, where they take a sample of fluid from your small intestine. This is expensive and often inaccurate though, so it’s rarely used.

About the test

You can take a SIBO test at home, or in a hospital or clinic. For the full lowdown on the SIBO testing experience, read our blog SIBO test: all your questions answered (2021).

Until recently, mainstream medicine didn’t accept that SIBO was a common condition, so you were extremely unlikely to get a SIBO test through the NHS. 

The US is a few years ahead of the UK on SIBO, but Dr. Hazel Veloso, gastroenterologist at Johns Hopkins University in the US, remembers when SIBO was rare: “We were just labelling patients with IBS before,” she says on the hospital’s website. “They were not getting better because there was actually an underlying cause.”

A huge amount of research over the last two decades has linked IBS symptoms to SIBO: up to 85% of IBS sufferers have been found to have SIBO [Source: PubMed].

As a result, more and more NHS trusts are now carrying out SIBO tests, which is great news. That means that you may be able to get a referral from your GP to a gastroenterologist, who can run a SIBO test at your nearest hospital. However, depending on your GP, getting an appointment could be difficult, or take a long time.

There are a few different types of SIBO breath tests. Most experts agree that a three-hour test that uses a l-lose solution to test for both hydrogen and methane is the most reliable and effective, but some NHS trusts and gastroenterologists still use a two-hour test. Some also use a glucose solution instead of l-lose, which has been shown to produce more false negative results [Source: PubMed].

It’s important to test for methane and hydrogen gases, as methane has been shown to produce symptoms in multiple studies. Constipation appears to be the most common symptom of methane SIBO [Source: PubMed].

At Healthpath we use the three-hour l-lose SIBO test, which measures both hydrogen and methane gases. You’ll receive the test kit within two to three days of your request. You’ll need to follow a special diet for the day before the test. 

You’ll get your results within a maximum of one week.

What does the SIBO test show?

The SIBO test shows the levels of hydrogen and methane gas present in your small intestine.

It does this by measuring those gases in your breath. It might seem strange that we measure gases in your gut by looking at the levels in your breath, but while 80% of this gas remains in your intestines, the other 20% is absorbed into your blood and travels round to your lungs—where you breathe it out [Source: PubMed].

By measuring the levels of gases in your breath, we can tell whether or not you have bacterial overgrowth in your small intestine.

Hydrogen levels

Some tests only show hydrogen levels. While it’s useful to know your hydrogen levels, that’s only one part of the picture. We know from the latest research that methane is just as likely to cause symptoms as hydrogen, so you need to know that too [Source: PubMed].

Evidence suggests that patients with high levels of hydrogen gas are more likely to have diarrhoea [Source: PubMed] than constipation, although it is possible to have high levels of hydrogen with constipation.

Methane levels

Most tests in the UK now measure both hydrogen and methane levels. Because the microbes that produce methane aren’t bacteria, a high level of methane in your small intestine is now officially called ‘intestinal methane overgrowth (IMO)’ [Source: Pub Med].

The organisms that produce methane are called archaea. The methane they produce has been shown to slow down gut transit time, resulting in constipation [Source: PubMed], although it is possible to have high methane levels and no constipation.

Test, don't guess. Try our hydrogen methane test.

View our at home SIBO test

SIBO breath test accuracy

Leading practitioners use the hydrogen/methane breath test for SIBO because overall, it gives the most accurate and reliable results [Source: Pub Med].

However, no test is perfect, and false negatives and false positives do happen. That means you could have SIBO, yet your test result is negative. Or, you could get a positive result when you don’t have SIBO. While this is unlikely to happen to you, it’s not impossible.

That’s why it’s vital to work with an experienced Functional Medicine Practitioner or Registered Nutritional Therapist to interpret your results. While the SIBO breath test is the most important tool you can use to confirm or rule out SIBO, your health history and symptoms are crucial parts of the picture too. 

When you buy a SIBO breath test from Healthpath, we ask you about your health history and your symptoms as part of the testing process. Your practitioner will use this information along with your test results to create your diet, supplement and lifestyle recommendations. Everything is included in the test price.

Understanding breath test results

Your results will appear on a graph, which can look a bit technical but you’ll also get a plain English translation, stating whether you have SIBO or you don’t.

The graph allows you to see which part of your gut is likely to contain the overgrowth (if the result is positive).

A peak in gases early on in the graph shows an overgrowth in the upper part of your small intestine, while one later on reflects a problem lower down, closer to your large intestine. 

It’s worth noting that everyone ‘should’ have a peak after the 120 minute mark, as this reflects gases in your large intestine, which is normal and healthy. If there is no peak at or after this point, your practitioner may suspect overgrowth from hydrogen sulphide producing bacteria. There are other signs and symptoms that could point towards this, which they can look for and investigate.

Results and treatment

Your results will fall into one of four categories:

Negative for SIBO

If you test negative, it’s possible that you have dysbiosis lower down in your large intestine, or a fungal overgrowth, which doesn’t show up on SIBO breath tests.

Positive for hydrogen overgrowth

Hydrogen is more likely to result in diarrhoea. Hydrogen SIBO has been shown to respond well to protocols using herbs like oregano or berberine [Source: Pub Med].

Positive for methane overgrowth

Methane is more likely to result in constipation. There’s evidence that allicin in garlic reduces the archaea that produce methane. This study was on sheep [Source: Pub Med] but it’s part of a standard protocol used by naturopathic doctors and practitioners for methane SIBO.

Positive for hydrogen and methane overgrowth

It’s possible to have both hydrogen and methane overgrowth. An experienced practitioner can create a protocol to reduce the microbes responsible for both these gases.

Key takeaways

  • A SIBO breath test is the most effective and common way to test for SIBO
  • You can ask your GP to refer you for a SIBO test, but it’s not always easy and may take a while
  • The test will show the levels of hydrogen and methane in your small intestine, but some tests only show hydrogen
  • Hydrogen levels reflect the numbers of bacteria in your small intestine
  • Methane levels reflect the numbers of archaea in your small intestine
  • SIBO breath tests are accurate but not perfect
  • It’s important to work with an experienced practitioner who will use the test results as a tool to build a picture of your general gut health

Author

Alexandra Falconer MA (Dist) DipCNM mBANT is a Registered Nutritional Therapist specialising in IBS and related conditions. A graduate of Brighton’s College of Naturopathic Medicine, she is committed to fighting the root causes of chronic illness and bringing functional medicine to everyone who needs it.

Before her natural health career, Alex was a journalist and copywriter. She continues to write for magazines and media agencies, and now combines her two great passions—writing and health—by creating content that empowers people to claim their right to a healthy body and mind.

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