False positives can occur with Carbon 13 Breath, especially due to the effects of related medications or if the test is performed after eating. Carbon 13 Breath requires fasting for at least 6 hours, cessation of antibiotics for at least 4 weeks, cessation of proton pump inhibitors and bismuth for at least 2 weeks, and cessation of related herbal medications before the test. False-positive results may occur if the carbon 13 breath test is performed without following the above requirements for preparation. In addition to false positives, there are also false negatives, such as when H. pylori is suppressed by the use of antibiotics prior to the test. There are many ways to test for H. pylori, such as gastroscopy with a rapid urease test, fecal examination, and serologic antibody testing. Patients who are suspected of having H. pylori infection can be further tested in the above ways. Patients who suspect false positive H. pylori on carbon 13 breath test need to consult a doctor for further testing.