H. pylori: testing, treatment and checking it has cleared

What can the infection cause?

Many people have no symptoms. In others, the infection contributes to inflammation or ulcers in the stomach or duodenum. It can increase the long-term risk of stomach cancer, but most infected people do not develop cancer. Treating infection reduces important future risks; it is not a promise that every digestive symptom will disappear.

H. pylori is often acquired in childhood. Spread is thought to occur mainly between people, often within households, through contact with infected saliva, vomit or traces of poo. Food or water contaminated by the bacteria can also transmit infection. The exact route is not always known. A positive test does not tell us when it was acquired and should not be treated as a judgement about current hygiene.

The chance of infection differs between communities and countries. After successful eradication, reinfection in adults is uncommon in higher-income settings. Studies often report less than 1% per year for a genuinely new infection, although rates vary between populations. A positive result soon after treatment can instead mean the original infection was not fully cleared.

Who should be tested?

I consider symptoms, previous ulcers, family history of stomach cancer, country of birth, childhood background and previous treatment. In New Zealand, infection is more common in Māori, Pacific and some Asian communities, but ethnicity alone does not diagnose infection or explain someone’s symptoms.

Not everyone with heartburn or bloating needs H. pylori testing, and antibiotics should not be prescribed on suspicion alone. Difficulty swallowing, bleeding, unexplained iron deficiency, weight loss or persistent vomiting may justify gastroscopy or another investigation rather than relying on a stool test alone. For adults aged 18 and over, testing is generally considered when relevant risk factors or clinical indications are present, rather than for every digestive symptom.

Paediatric guidelines generally advise against routine 'test-and-treat' testing in children because the aim is usually to find the cause of symptoms, and H. pylori is not usually the cause of symptoms without an ulcer. Testing is considered when a child has a gastric or duodenal ulcer or another clear clinical reason.

Why an antibody test cannot show current infection

A stool antigen test looks for evidence of current infection. A urea breath test can also detect active infection. If gastroscopy is indicated, stomach biopsies can be tested.

Gastroscopy can also assess complications such as ulcers or changes in the lining and, in some circumstances, provide samples for culture to help tailor antibiotic treatment. It is not necessary for everyone just to find H. pylori.

A blood antibody test can remain positive after an old infection has cleared. It is therefore generally unsuitable for confirming active infection or treatment success. A negative stool or biopsy result also needs context if medicines have temporarily suppressed the bacteria.

Medicines can make the test falsely negative

For stool antigen testing, current guidance uses a gap of at least two weeks without a proton pump inhibitor (PPI), such as omeprazole or pantoprazole, and at least four weeks without antibiotics or bismuth. The same timing is relevant when checking eradication. Taking these medicines too close to testing can hide an infection.

Agree this with your prescriber before changing treatment. Do not stop necessary prescribed medicine from an online checklist, particularly if you have had an ulcer or bleeding. Tell us about recent antibiotics and ask how to control symptoms safely while preparing for the sample.

Why treatment is not the same for everyone

Treatment combines acid suppression with antibiotics, sometimes with bismuth. I check previous antibiotic exposure, allergies, interactions and pregnancy or breastfeeding before selecting a course. Your prescription will state the exact medicines, doses and duration.

Completing the full prescribed course gives the best chance of clearing H. pylori. Stopping early or missing doses can leave infection behind and may encourage antibiotic resistance, making later eradication attempts more difficult. If side effects are troublesome, contact me or the prescribing clinician promptly rather than stopping treatment on your own.

Antibiotic side effects are usually mild and temporary. Taking each medicine at the prescribed time, with food when the instructions allow, can help. Small, regular meals, plenty of fluids and avoiding alcohol during treatment may improve tolerance.

Some probiotics may reduce antibiotic-related diarrhoea, but results vary and there is not enough consistent evidence to recommend a particular product routinely. They are optional and do not replace the prescribed treatment; check with your clinician or pharmacist if you are immunocompromised, pregnant or taking other medicines.

Check that treatment worked

I usually arrange a faecal antigen test 6 to 8 weeks after treatment to confirm clearance, even if you feel better. Leave at least four weeks after antibiotics or bismuth and two weeks without a PPI, with an agreed medicine plan. An antibody blood test cannot confirm clearance.

If infection remains, I review which medicines were taken, missed doses, side effects and antibiotic history before considering another regimen or specialist testing. Persistent infection is not proof that you have cancer, and repeating the same course without review may fail again.

What if symptoms persist after the infection has cleared?

Discomfort can continue even after H. pylori has cleared. Reflux, functional dyspepsia, an ulcer that needs further care or another condition may be responsible. I review your symptoms and previous results before recommending more treatment.

If gastroscopy found an ulcer or a change such as intestinal metaplasia, its follow-up is considered separately from the test of cure. The recommended follow-up will be documented in your endoscopy and/or histology report once tissue results are available. Household testing is also an individual decision; do not share antibiotics.

Related information

• Reflux and oesophagitis
• Biopsies after endoscopy
• Understanding your tissue report
• Gastritis and reactive gastropathy