Urea breath tests are recommended in leading society guidelines as a preferred non-invasive choice for detecting H. pylori before and after treatment.

[1][2] Patients swallow urea labelled with an uncommon isotope, either radioactive carbon-14 (nowadays preferred in many countries) or non-radioactive carbon-13.

In the subsequent 10–30 minutes, the detection of isotope-labelled carbon dioxide in exhaled breath indicates that the urea was split; this indicates that urease (the enzyme that H. pylori uses to metabolize urea to produce ammonia) is present in the stomach, and hence that H. pylori bacteria are present.

Alternatively, NDIR spectrometry can be performed by a table-top instrument as an office-based test, and results are provided immediately within minutes.

[7] The test is especially done accompanying an eradication therapy by antibiotics (to avoid overdosing) or to check the success of an ulcer operation.