Having taken omeprazole to check H. pylori is likely to affect the accuracy. Omeprazole is an acid-suppressing drug. After taking omeprazole, stomach acid is suppressed and the PH value will rise, which is temporarily unfavorable for bacterial growth, and the test for H. pylori is likely to show a false-negative result, which will lead to a missed diagnosis. If you are taking Omeprazole, it is generally recommended to stop the medication for 2 weeks to test for H. pylori. Moreover, other medications for treating gastric disorders, such as bismuth, antibiotic medications such as bismuth potassium citrate, cephalosporins, and levofloxacin need to be paused for 4 weeks, to avoid affecting the accuracy of the test results. It is recommended to consult with your doctor about the preparations before the H. pylori test, and cooperate with your doctor for treatment or therapy according to the results after the test.