Helicobacter pylori (H. pylori) Testing: Understanding Your Report

Section Editor: Rodney E. Rohde PhD
June 4, 2026

Helicobacter pylori, usually shortened to H. pylori, is a bacterium that infects the lining of the stomach. A bacterium is a microorganism, a living thing too small to see without a microscope. H. pylori is very common, and many people who carry it have no symptoms. In others, it can cause inflammation of the stomach lining, ulcers in the stomach or upper intestine, and, over time, increase the risk of certain stomach cancers.

This article explains the different tests used to check for H. pylori, what the wording on your report means, and an important difference among the tests, which is whether they show a current infection or only that you were infected at some point, so you can better understand a report you have received.

What is H. pylori, and why test for it?

H. pylori lives in the lining of the stomach. Inflammation of that lining is called gastritis; when it is caused by this bacterium, it may be reported as Helicobacter gastritis. Open sores in the lining of the stomach or the upper intestine are called peptic ulcers, and H. pylori is a common cause of both. Over many years, a long-standing infection also raises the risk of certain stomach cancers, including adenocarcinoma. Finding and treating H. pylori can heal ulcers, ease symptoms, and lower these risks, which is why testing is done when an infection is suspected.

Tests that show a current (active) infection

Most H. pylori tests are designed to show whether you have an infection right now. These are the tests used both to diagnose an active infection and to confirm that treatment has worked.

Urea breath test — You swallow a harmless substance, and the test then measures your breath. If H. pylori is present, it breaks the substance down in a way that shows up in your breath. It detects a current infection and does not require a blood draw or a procedure.
Stool antigen test — Looks for pieces (antigens) of H. pylori in a stool sample. It also detects a current infection.
Tests on a biopsy — During an upper endoscopy (a procedure in which a thin camera is passed into the stomach), small tissue samples (biopsies) can be taken and tested for H. pylori. These include a rapid test for the bacterium’s enzyme, a pathologist’s microscopic examination (which also shows the condition of the stomach lining), and sometimes a culture or molecular test to determine which antibiotics will work.

The blood antibody test and its limitations

The blood test, also called serology, looks for antibodies your immune system makes against H. pylori. Antibodies, and the difference between this kind of test and tests that detect the germ itself, are explained in the article on PCR, antigen, and antibody tests. A positive antibody test means you have been infected at some point, but it has an important limitation: antibodies can remain in the blood for a long time after the infection is gone, so this test cannot tell a current infection from a past one. For the same reason, it is not used to confirm that treatment has worked. Its one advantage is that, unlike the active-infection tests, it is not affected by the medications described in the next section.

Medications that can affect your result

Several common medications can cause active-infection tests (breath, stool, and biopsy tests) to come back falsely negative by lowering H. pylori levels below the test’s detection limit. These include acid-reducing medicines called proton pump inhibitors, antibiotics, and bismuth, which is found in some stomach remedies. For this reason, your doctor may ask you to stop these for a period before testing, often about two weeks for acid-reducing medicines and about four weeks for antibiotics or bismuth. The blood antibody test is not affected in this way.

How to read your result

The meaning of your result depends mainly on whether the test shows a current infection or past exposure.

A positive active-infection test (breath, stool, or biopsy) — A current H. pylori infection is present, and treatment is usually recommended.
A negative active-infection test — No current infection was found. If you recently took acid-reducing medicines, antibiotics, or bismuth, a negative result may need to be repeated after stopping them.
A positive blood antibody test — You have been infected with H. pylori at some point, but this does not tell you whether the infection is current. An active-infection test may be needed to confirm.
A negative blood antibody test — An H. pylori infection is unlikely.

What happens after these tests

An H. pylori test describes what was found, and it informs the decisions you and your healthcare team make together rather than dictating them on its own.

A current infection is usually treated with a combination of antibiotics together with a medicine that reduces stomach acid, taken for a set number of days. Because H. pylori is increasingly resistant to some antibiotics, your doctor may use susceptibility testing, which checks which antibiotics will work, as explained in the article on culture and sensitivity testing, to guide treatment, especially if a first round does not clear the infection. After treatment, a test is usually done to confirm the infection is gone, using an active-infection test such as a breath or stool test rather than a blood antibody test, generally at least 4 weeks after finishing antibiotics and after stopping acid-reducing medicines. If a biopsy was taken, what it shows about the stomach lining may guide further follow-up.

Questions to ask your doctor

Which H. pylori test did I have, and does it show a current infection or only past exposure?
If my blood test was positive, do I need another test to confirm whether the infection is active now?
Could a medication I am taking, such as an acid reducer or an antibiotic, have affected my result?
Should I stop any medications before testing, and for how long?
If I have an active infection, what does treatment involve?
Could antibiotic resistance affect my treatment, and is susceptibility testing needed?
How and when will we confirm the infection is gone after treatment?
If I had a biopsy, what would it have shown about my stomach lining?
Does this infection change my risk of ulcers or stomach cancer, and what follow-up do I need?
Who should I contact with questions about my results or treatment?