The 14C-urea breath test is used to assess the effectiveness of treatment for Helicobacter pylori (H. pylori) infection. The test involves swallowing a capsule containing 14C-labeled urea, which is metabolized by any remaining H. pylori bacteria into 14CO2 that is exhaled and can be detected. A result over 200 cpm indicates H. pylori is still present, while under 50 cpm indicates treatment was effective in eradicating the infection. The test provides accurate results one month after treatment completion to verify treatment success or failure.