The Carbon-13 Urea Breath Test (C-13 UBT) is a diagnostic method used to detect H. Pylori infection in the stomach, which is a major cause of duodenal ulcers—affecting the upper intestine connected to the stomach. H. Pylori is a risk factor for several conditions, including gastritis, stomach ulcers, and stomach cancer.

The test involves measuring labeled carbon dioxide (13 CO2), which is a byproduct of urea breakdown by the enzyme urease, produced by H. Pylori. After ingestion of the urea solution, if H. Pylori is present, urease will break down the urea, resulting in the production of 13 CO2. This labeled carbon dioxide then enters the bloodstream and is eventually exhaled through the lungs, where it can be measured to confirm the presence of the infection.