The reference range for a Carbon 13 test result is generally less than 4 dpm. Carbon 13 refers to the Carbon 13 Breath Test, which is often used to check for H. pylori infection, and the normal range is generally 0 to 4 dpm. if the test result is less than 4, it means that the H. pylori test result is negative, which means that H. pylori infection does not exist. If the carbon 13 breath test result is greater than or equal to 4 dpm, it means that the H. pylori test result is positive, which means that H. pylori infection is present. In addition to the carbon 13 breath test, a carbon 14 breath test can also be done, which can also be used to detect H. pylori. If you suspect the presence of H. pylori infection, you must go to the hospital in time, cooperate with the doctor to take the relevant tests, and then take active treatment after a clear diagnosis.