Urea Breath Test (UBT) for H. Pylori: How It Works, Preparation & Results

A urea breath test (UBT) is a non-invasive breath test that detects active H. pylori infection in the stomach. You drink a urea solution, and if H. pylori is present, its urease enzyme breaks the urea into carbon dioxide, which you exhale and a lab measures 10–30 minutes later.

A urea breath test (UBT) is a breath-based diagnostic test used to identify an active H. pylori infection. UBT stands for urea breath test, which is why the test may also appear in searches and laboratory listings as a "UBT test" or "H. pylori breath test".

Unlike an endoscopy, UBT does not require a camera to be passed into the stomach, sedation or tissue biopsy, making it a convenient non-invasive option for many patients.

The test uses urea labelled with either carbon-13 (¹³C) or carbon-14 (¹⁴C). Carbon-13 is a stable, non-radioactive isotope, while carbon-14 involves a very small amount of ionising radiation and is generally reserved for appropriate adult use; ¹³C testing is generally preferred when avoiding radiation is important.

Pregnant and lactating women should discuss the appropriate test with their doctor, and a ¹⁴C test should not be selected during pregnancy when a non-radioactive alternative is available.

Evidence from diagnostic meta-analyses shows that both methods can provide high diagnostic accuracy, although recent evidence found somewhat higher specificity for ¹³C UBT.

The procedure itself is usually quick. Depending on the laboratory protocol, the complete test may take around 20–30 minutes, while results may be available the same day or after the sample has been processed by a laboratory, depending on the provider.

For convenient diagnostic testing, patients can check UBT availability with MyDiagnostics and discuss the appropriate testing option with a healthcare professional.

Helicobacter pylori, commonly called H. pylori, is a spiral-shaped bacterium that can colonise the stomach lining and persist for many years if it is not eradicated. It is one of the most common chronic bacterial infections worldwide, although prevalence varies considerably between countries and populations.

A large global meta-analysis covering data up to 2022 estimated that approximately 43.1% of people worldwide were infected during 2011–2022, with substantial regional variation.

Many people with H. pylori have no obvious symptoms, but infection can contribute to chronic gastritis, indigestion, upper abdominal discomfort, nausea, bloating, and stomach ulcers. H. pylori is also an established risk factor for gastric cancer, particularly non-cardia gastric cancer, although infection does not mean that an individual will develop cancer.

The International Agency for Research on Cancer (IARC), part of WHO, has identified H. pylori as an important cause of infection-related cancer and has estimated a substantial proportion of non-cardia gastric cancers to be attributable to the bacterium.

Untreated infection can therefore matter even when symptoms are mild or absent. Confirming infection with an appropriate H. pylori stool antigen test allows clinicians to decide whether eradication treatment is indicated rather than assuming that stomach symptoms are caused by H. pylori.

The American College of Gastroenterology (ACG) recommends treating patients who are found to be infected and subsequently confirming eradication with an appropriate helicobacter pylori test.

The urea breath test procedure is based on a simple biochemical reaction involving the urease enzyme produced by H. pylori. The patient first provides a baseline breath sample, drinks or swallows labelled urea, and then provides another breath sample after a short waiting period.

The laboratory compares the breath samples to determine whether labelled carbon dioxide has been produced.

The procedure generally begins with the patient breathing into a collection tube, bag or other approved container before taking the labelled urea. This first sample establishes the amount of the relevant carbon isotope present in the patient's breath before the test substance is administered.

Establishing this baseline is important because the final measurement is interpreted by comparing it with the post-urea sample.

The collection itself is painless and does not require needles, anaesthesia or sedation. Patients simply follow the laboratory technician's instructions for breathing into the collection device. The exact collection method varies between manufacturers and laboratories.

The patient then swallows a small amount of urea containing a labelled carbon isotope, usually ¹³C or ¹⁴C. Depending on the testing system, the urea may be supplied as a capsule, liquid, tablet or flavoured preparation.

Some commercial kits use a citrus-flavoured drink or another formulation designed to make the preparation easier to swallow.

The labelled urea itself is not intended to treat the infection. Instead, it provides the substance needed to reveal whether H. pylori urease is present in the stomach. The patient then waits for the prescribed interval before providing the second breath sample.

The key to the H. pylori urease test is an enzyme called urease. H. pylori produces urease to help it survive the highly acidic environment of the stomach; the enzyme breaks down urea into ammonia and carbon dioxide. When the administered urea contains ¹³C or ¹⁴C, the resulting carbon dioxide also contains the labelled carbon isotope.

This explains why the test may sometimes be described informally as an ammonia breath test or urease breath test. However, an important distinction is that the breath test primarily measures the labelled carbon dioxide, not ammonia directly.

If H. pylori is absent, there is no significant bacterial urease reaction to generate the expected increase in labelled carbon dioxide.

After the required waiting period, usually around 10–30 minutes depending on the test kit and laboratory protocol, the patient provides a second breath sample.

The labelled carbon dioxide produced in the stomach enters the bloodstream and is transported to the lungs. It is then exhaled and captured in the collection device for analysis.

The exact timing is important because different UBT systems use different doses, collection intervals and analytical methods.

Research indicates that factors such as urea dose and breath collection timing can influence diagnostic performance, so patients should follow the instructions provided by the laboratory rather than using a generic timing schedule.

The laboratory compares the baseline and post-urea breath samples to determine whether there has been a significant increase in labelled carbon dioxide. For ¹³C UBT, the isotope ratio may be measured using techniques such as infrared spectroscopy or isotope-ratio mass spectrometry. For ¹⁴C UBT, the emitted radioactivity can be measured using scintillation-based techniques.

A significant rise in labelled carbon dioxide supports the presence of active H. pylori infection. If there is no meaningful increase, the result is generally interpreted as negative, although medications, recent treatment and other clinical circumstances can affect accuracy.

Correct preparation is essential because some medicines can suppress H. pylori or its urease activity and cause a false-negative UBT result.

The most important preparation requirement is medication washout, particularly for proton pump inhibitors (PPIs), antibiotics and bismuth-containing medicines. Always follow the specific instructions given by the testing laboratory and prescribing doctor.

The 2024 ACG guideline specifically advises holding PPIs for 2 weeks and antibiotics and bismuth for 4 weeks when performing a test of cure.

PPIs reduce stomach acid and can suppress the density or activity of H. pylori, while antibiotics and bismuth can directly reduce bacterial numbers. If the organism is temporarily suppressed, it may not produce enough urease to generate the labelled carbon dioxide required for a positive test.

As a result, testing too soon after treatment or while taking certain medicines may incorrectly suggest that the infection is absent.

Patients should not stop prescription medicines without medical advice. If a PPI or another medicine cannot safely be discontinued, the doctor may recommend postponing the test or using an alternative diagnostic strategy.

A positive UBT generally indicates an active Helicobacter pylori infection because the test detects the metabolic activity associated with live urease-producing bacteria.

A doctor will typically discuss eradication treatment based on the patient's history, previous antibiotic exposure, allergies and local resistance considerations. Current ACG guidance recommends treatment for patients found to have H. pylori infection.

A negative result means that the test did not detect evidence of active Helicobacter pylori infection. However, a negative result is not always definitive if the patient recently used PPIs, antibiotics or bismuth, or if another factor has reduced test sensitivity.

If symptoms persist despite a negative result, the doctor may consider repeat testing or another diagnostic approach.

UBT is considered one of the most accurate non-invasive tests available for H. pylori. A 2015 meta-analysis reported pooled sensitivity of approximately 96% and specificity of approximately 93%, while a 2024 meta-analysis reported very high diagnostic performance for both ¹³C and ¹⁴C UBT, with ¹³C showing sensitivity of about 96.6% and specificity of about 96.9% in the analysed studies.

False-negative UBT results are more likely when testing is performed too soon after antibiotics, bismuth or acid-suppressing treatment. A recent bleeding peptic ulcer can also reduce the sensitivity of some H. pylori diagnostic methods, so the clinical setting matters when interpreting results.

False-positive results are less common with a properly performed UBT but can occur because of technical factors, protocol differences or other urease-producing organisms in certain clinical circumstances. This is why the result should be interpreted together with the patient's symptoms, medical history and test preparation.

One of the most important uses of UBT is confirming whether H. pylori has actually been eradicated after treatment. Symptoms alone cannot reliably establish eradication, because stomach discomfort may persist even after successful treatment or may have another cause.

The ACG recommends performing a test of cure at least four weeks after therapy, using a urea breath test, stool antigen test or appropriate biopsy-based test, with PPIs withheld for two weeks and antibiotics/bismuth for four weeks when clinically feasible.

Several tests can detect H. pylori, but they do not all answer the same clinical question. UBT and stool antigen testing are generally useful non-invasive methods for detecting active Helicobacter pylori infection, whereas blood antibody testing can remain positive after the infection has cleared.

Endoscopic biopsy testing can provide additional information about the stomach but is invasive and is generally selected when endoscopy is indicated for another clinical reason.

Both UBT and stool antigen testing are non-invasive tests that can detect active H. pylori infection and can be used after treatment to assess eradication. UBT has the advantage of requiring only a breath sample, whereas stool antigen testing requires collection of a stool specimen.

The choice may depend on availability, cost, patient preference, age, clinical circumstances and local laboratory practice.

A blood test can detect antibodies against H. pylori, but antibodies may remain detectable after the bacteria have been eradicated. Therefore, serology cannot reliably distinguish a current infection from previous exposure. This is one reason non-invasive tests that detect active infection, such as UBT or stool antigen testing, are generally preferred when confirming current infection or treatment success.

An endoscopy allows a doctor to directly examine the upper digestive tract and collect stomach tissue for rapid urease testing, histology or other laboratory analysis. It can therefore provide information that a breath test cannot, such as ulcers, bleeding, gastritis or suspicious lesions.

However, endoscopy is invasive and may require sedation, so UBT is often more appropriate when the primary clinical question is simply whether active H. pylori infection is present.

The major benefit of UBT is that it detects active infection without requiring an endoscopic procedure. It is generally quick, painless and highly accurate, and it can be repeated when necessary, including for post-treatment confirmation. Its high diagnostic performance has been demonstrated in multiple systematic reviews and meta-analyses.

Another advantage is that the test does not require tissue removal or sedation. This can make it particularly useful for patients who have symptoms suggestive of H. pylori but do not otherwise require endoscopy. It is also useful for a test of cure, which is an important part of modern H. pylori management.

However, UBT has limitations. Patients usually need to stop certain medicines before testing, which may not always be possible or convenient, and the ¹⁴C version involves a small amount of radiation. Availability and pricing can also vary between laboratories, and test protocols differ between manufacturers.

• Non-invasive and painless

• No endoscopic camera or tissue biopsy required

• Usually completed within approximately 20–30 minutes

• High sensitivity and specificity

• Detects active rather than merely historical infection

• Can be used to confirm eradication after treatment

• Does not require sedation

• Suitable for repeat testing when clinically indicated

• PPIs may need to be stopped for approximately two weeks

• Antibiotics and bismuth generally need a four-week washout

• ¹⁴C testing uses a small amount of radioactivity

• ¹³C and ¹⁴C protocols are not identical

• Availability varies between centres

• Cost and insurance coverage can vary

• Results can be affected by incorrect preparation

If you are looking for reliable diagnostic testing, MyDiagnostics can help you explore available testing options and laboratory services, subject to local availability and medical advice.

A doctor may recommend a urea breath test when H. pylori infection is suspected and a non-invasive test is appropriate. It may be considered in people with persistent dyspepsia, unexplained upper abdominal discomfort, suspected peptic ulcer disease or other clinical circumstances in which testing for H. pylori is appropriate.

NIDDK lists UBT and stool testing among the non-invasive approaches used to detect H. pylori. UBT is particularly valuable when the objective is to determine whether active infection is present rather than whether the person has ever been exposed to the bacterium.

It is also a strong option for confirming eradication after treatment because it measures bacterial urease activity rather than relying on persistent antibodies.

• People with persistent or unexplained indigestion or upper abdominal discomfort

• Patients with suspected or confirmed peptic ulcer disease

• People with a previous H. pylori infection who require confirmation of eradication

• Patients for whom a non-invasive active-infection test is preferred

• Patients who do not otherwise require upper GI endoscopy

• People whose doctor is evaluating persistent gastrointestinal symptoms after considering other causes

A family member of a person with H. pylori should not automatically assume that a UBT is required solely because another household member tested positive. H. pylori can spread between people, but the decision to test should be based on individual risk, symptoms, medical history and current clinical recommendations rather than self-testing alone.

UBT is often attractive when a doctor needs a non-invasive, highly accurate test for active infection and there is no separate reason to perform an endoscopy. Stool antigen testing can provide a similarly useful alternative, particularly when UBT is unavailable, or stool testing is more practical.

Endoscopy may be preferred when there are alarm features, suspected complications, significant bleeding or another reason to inspect the stomach directly. The final choice therefore depends on the patient's age, symptoms, medical history, medication use and the reason for testing rather than on UBT being universally superior to every other test.

The urea breath test (UBT) is a simple, non-invasive and highly accurate way to detect active H. pylori infection. It works by using labelled urea to reveal the urease activity of H. pylori, with the resulting labelled carbon dioxide measured in the patient's breath. Proper preparation is essential because PPIs, antibiotics and bismuth can reduce test accuracy and produce false-negative results.

UBT is also particularly useful as a test of cure after H. pylori treatment. Current ACG guidance recommends confirming eradication at least four weeks after therapy using UBT, stool antigen testing or an appropriate biopsy-based test, while observing the recommended medication washout periods.

If you have persistent digestive symptoms or have recently completed H. pylori treatment, speak with your doctor about whether a UBT or another active-infection test is appropriate. MyDiagnostics can be considered for diagnostic testing options where UBT services are available, with test selection and interpretation guided by a qualified healthcare professional.