Hydrogen Breath Test: What Is It and What Can It Detect?

A hydrogen breath test (HBT) is a simple, non-invasive test used to investigate certain digestive problems, such as small intestinal bacterial overgrowth (SIBO) and lactose/fructose intolerance.

The test measures the hydrogen and methane gas in your breath after you drink a solution containing a specific sugar. Depending on the type of test, hydrogen and methane levels are measured to see how your body processes the sugar.

A hydrogen breath test usually requires a period of fasting before the test. Here, we explain what a hydrogen breath test is, when it may be recommended, and what it can detect.

What is the Hydrogen Breath Test (HBT)?

A hydrogen breath test, or hydrogen-methane breath test, is a non-invasive diagnostic tool to detect SIBO, IBS, and intolerance to lactose, fructose, or sucrose sugars. The test evaluates your digestion of particular sugars by measuring the gas (hydrogen or methane) in your exhaled breath. Different types of hydrogen breath tests use different sugars. These include lactose, fructose, glucose, sucrose, and sorbitol. The results help identify problems with sugar digestion or bacterial overgrowth in the small intestine. 

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Who Should Have a Hydrogen Breath Test?

A healthcare professional may recommend a hydrogen breath test if you have ongoing digestive symptoms that could be linked to SIBO or carbohydrate malabsorption. Common symptoms include:

• Abdominal tightness or discomfort 
• Changes in bowel habits
• Diarrhea after drinking milk or consuming dairy products
• Excessive gas or bloating

What Can a HBT Diagnose?

Sometimes, digestive issues can cause abnormal hydrogen levels in the gut, which can be measured in your breath. It helps healthcare providers diagnose the following health issues:

SIBO

SIBO (Small Intestinal Bacterial Overgrowth) is a digestive condition in which helpful bacteria from your colon move to the small intestine. Under healthy conditions, most gut bacteria live in the large intestine. When bacteria build up in the small intestine, they ferment food too early and produce gases, which may lead to bloating, abdominal discomfort, excessive gas, and changes in bowel habits. A hydrogen and methane breath test can help investigate SIBO by measuring changes in these gases after a person drinks a test solution. 

Intolerance to Sugars

A hydrogen breath test can also help identify carbohydrate malabsorption. This happens when the digestive system does not properly absorb a particular sugar.

The HBT screening is used to investigate digestive problems associated with:

• Lactose, found in milk and dairy products
• Fructose, found in fruits and some other foods
• Sucrose, commonly known as table sugar

Lactose intolerance is one of the most common reasons for having a hydrogen breath test. If lactose is not properly digested, it can reach the colon, where bacteria ferment it and produce gas. It can cause bloating, abdominal pain, gas, and diarrhoea.

How to Prepare for a Hydrogen Breath Test?

For an HBT test, you need to follow some instructions to get accurate results. These are:

• Brush your teeth at least 2 hours before the test.
• Fast for around 12 hours before the test. 
• Avoid smoking and alcohol before the test.
• Avoid strenuous exercise before and during the test.
• Stay awake for at least 1 hour before the test.
• Avoid tea and coffee before the test. If permitted by your test provider, have them without milk or sugar.
• Avoid laxatives and antibiotics for the period advised by your test provider. However, don’t stop any prescribed medication without speaking to your doctor first.

The Procedure Involved in a Hydrogen Breath Test

You will first provide a breath sample by breathing into a collection bag. You will then drink a solution containing a specific sugar, such as lactose, fructose, or lactulose, depending on the type of test. Further breath samples will be collected at regular intervals, usually every 15 to 30 minutes. The samples are analysed to measure the levels of hydrogen and methane in your breath.

The test usually takes around 2 to 4 hours. During this time, tell the technician if you develop any symptoms, such as bloating, abdominal pain, gas, or diarrhoea. You can easily leave and return to your normal diet once all the required breath samples have been collected. 

Types of Hydrogen Breath Test

There are different types of hydrogen breath tests. The choice of test depends on what your healthcare provider wants to investigate based on your symptoms.  

Lactose, Fructose, and Sucrose Intolerance Tests

These tests investigate whether your body is properly digesting specific sugars. Your doctor may recommend one of these tests based on your symptoms. A positive result may indicate that the particular sugar is not being properly absorbed. 

Glucose Breath Test

This test is commonly used to investigate SIBO. Glucose is quickly absorbed in the small intestine. If bacteria ferment the glucose and produce hydrogen before it is absorbed, this may indicate an increased number of bacteria in the small intestine. 

Are There Any Side Effects of the Test?

You can expect certain side effects of the hydrogen breath test, such as:

• Vomiting
• Nausea
• Stomachache
• Abdominal Discomfort

Hydrogen Breath Test Results and Interpretation

The normal level of hydrogen in the digestive system is less than 16 ppm. More than 20 ppm over the baseline is considered a positive test. The rise in hydrogen level by 20 ppm above the baseline must occur within 90 minutes, as hydrogen is being fermented in the small intestine instead of the colon. Strictly following the pre-test guidelines is essential to ensure accuracy and reliability of the HBT screening. 

Conclusion

A hydrogen breath test can help investigate digestive symptoms such as bloating, gas, abdominal discomfort, and diarrhoea. Depending on the test, it helps identify lactose or fructose malabsorption and investigate SIBO.

If you are experiencing symptoms after consuming dairy or fructose-rich foods, the right breath test can provide useful information about how your body processes these sugars.

The National Blood Test Clinic offers Lactose Intolerance and Fructose Intolerance Breath Tests across the UK. Book your lactose or fructose breath test today for fast, reliable results.