How does omeprazole 40mg affect urea breath test?

False Negative . Performing a urea breath test while being treated with a proton pump inhibitor (ppi) such as omperazole or other anti-secretory agents can cause a false negative result (h. Pylori may be present but goes undetected). If for some reason the test was performed while on a ppi and results are positive, its considered a true positive. For best results, stop ppi for 10-14 days before the test.