The difference between carbon 13 and carbon 14 urea breath test mainly includes labeled isotopes and analysis methods. 1. Labeled isotope: Urea is a normal product of human metabolism, the required nuclide is carbon 13 and carbon 14 labeled urea, carbon 13 is a non-radioactive isotope of carbon, which is very stable and harmless to the human body; carbon 14 is a radioactive isotope of carbon, which is radioactive to a certain extent, but its radiation is extremely small. 2. Analysis method: Carbon 13 is analyzed by nuclide mass spectrometry, which is also the more widely used method in clinical practice; Carbon 14 is detected by liquid flash counter. When the patient has severe lung disease, there may be a risk of examination, and should be considered with caution. Consult your physician for specific tests.