H. pylori (Helicobacter pylori) is a spiral-shaped bacterium that lives in the lining of the stomach. It is usually caught in childhood and can stay for life. Most people with H. pylori never have symptoms, but the infection keeps the stomach lining inflamed (gastritis) and is a leading cause of stomach ulcers and stomach cancer.
The good news: H. pylori is easy to detect with a breath test, a stool test or an endoscopy biopsy, and it is curable with 14 days of antibiotics plus an acid-reducing medicine. US gastroenterologists say everyone who tests positive should be treated; in the UK, a GP usually arranges a breath or stool test, then retested at least four weeks later.
Below: symptoms, which test to choose and how to prepare, the 2024 treatments, the links with anaemia and stomach cancer, and the latest research.
Key takeaways
- About 30% to 40% of people in North America and 44% of adults worldwide carry H. pylori; most feel nothing.
- The urea breath test, stool antigen test and stomach biopsy show an active infection; a blood antibody test does not.
- Stop proton pump inhibitors 2 weeks, and antibiotics and bismuth 4 weeks, before a breath or stool test (the NHS gives similar advice).
- First-choice treatment in the 2024 US guideline is bismuth quadruple therapy for 14 days; rifabutin triple therapy and vonoprazan-based therapy are alternatives.
- Curing the infection treats ulcers and lowers the risk of stomach cancer, so always do the test of cure.
What is H. pylori?
H. pylori is a bacterium adapted to survive in stomach acid. It produces an enzyme called urease, which breaks down urea into carbon dioxide: the chemistry the breath test detects.
Once in place, H. pylori keeps the stomach lining inflamed (chronic gastritis). Strains that make a toxin called CagA are more strongly linked with stomach cancer, according to the National Cancer Institute. The World Health Organization classifies H. pylori as a group 1 (definite) carcinogen, and the 2022 Maastricht VI/Florence consensus treats it as an infectious disease that should always be treated.
A 2024 meta-analysis of 1,748 studies from 111 countries found that 43.9% of adults worldwide were infected between 2015 and 2022, down from 52.6% before 1990. In children and adolescents it was 35.1%. The American College of Gastroenterology (ACG) estimates the prevalence in North America at 30% to 40%.
How H. pylori spreads and who is at risk
How H. pylori passes between people is not fully known. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says it may spread through an infected person's saliva, vomit or stool, or through food or water contaminated with them. Most infections start in childhood.
It clusters in families: in a 2026 study of 193 households in Vietnam, 58% of children with two infected parents had H. pylori, against 38.2% with one. The ACG suggests testing adult household members of a person with H. pylori.
The risk is higher if you:
- grew up in crowded housing or with poor sanitation;
- were born in, or immigrated from, a region where H. pylori and stomach cancer are common;
- are Black or Hispanic in the US: around 1999-2000, 52% of non-Hispanic Black and 64% of Mexican American adults were infected, against 21% of non-Hispanic white adults (National Cancer Institute).
H. pylori symptoms and warning signs
MedlinePlus notes that H. pylori usually causes no symptoms. When it does, they come from gastritis or an ulcer:
- a dull or burning pain in the upper belly, between the navel and the breastbone, often when the stomach is empty;
- bloating, burping and feeling full too soon;
- nausea, sometimes vomiting, and loss of appetite;
- unexplained weight loss.
Pain on an empty stomach has other causes; our guide to nausea when hungry helps sort them out.
Symptoms of H. pylori infection in children
Cleveland Clinic estimates that only 5% to 10% of infected children have symptoms, mostly belly pain, nausea or vomiting. A 2025 meta-analysis found higher odds of iron deficiency (odds ratio 1.52) and iron-deficiency anaemia (1.83) in infected children.
What H. pylori can lead to
Most people with H. pylori never develop a complication, but the infection is behind several diseases:
- Peptic ulcers. H. pylori and anti-inflammatory painkillers (NSAIDs such as ibuprofen, naproxen or aspirin) are their two most common causes, and combining them adds to the risk.
- Stomach cancer. The National Cancer Institute states that the majority of gastric adenocarcinomas are attributed to H. pylori. See our guide to stomach cancer symptoms and causes.
- Gastric MALT lymphoma, a rare lymphoma of the stomach (about 1 case per 100,000 people per year in the US). Nearly all patients show signs of H. pylori, and antibiotics can shrink these tumors. See lymphoma symptoms and tests.
- Iron-deficiency anaemia. Infected people have higher odds of iron-deficiency anaemia (pooled odds ratio 1.72 in a meta-analysis), and adding eradication therapy to iron raised ferritin more than iron alone.
- Immune thrombocytopenia (ITP), an immune low platelet count. In a systematic review, platelets rose after eradication therapy in 51.2% of H. pylori-positive patients, against 8.8% of negative ones.
- Autoimmune gastritis and vitamin B12. Autoimmune gastritis affects about 3.85% of people and is more frequent where H. pylori is common (2025 meta-analysis); its late stage, pernicious anaemia, causes B12 deficiency. A direct link between H. pylori and low B12 is less clear.
A possible link with bowel cancer is discussed in our news analysis of the H. pylori test and colon cancer.
Who should get an H. pylori test?
The 2024 ACG guideline lists the situations in which testing is recommended:
- indigestion (dyspepsia) before age 60 without alarm features, or before 50 if at high risk of gastric cancer;
- a current or past peptic ulcer, long-term NSAID use, or before starting daily aspirin;
- unexplained iron-deficiency anaemia, or immune thrombocytopenia (ITP);
- adult household members of someone with H. pylori;
- a family history of gastric cancer, immigration from a high-incidence region, or a high-risk race or ethnicity;
- precancerous stomach changes (atrophy, intestinal metaplasia, dysplasia), autoimmune gastritis, gastric MALT lymphoma or gastric polyps.
Indigestion with alarm features (bleeding, vomiting, unexplained weight loss, iron deficiency), NSAID use or a family history of gastric cancer calls for an endoscopy with biopsies instead.
H. pylori tests: breath, stool, blood and endoscopy
Some tests show an active infection; one only shows that you met the bacterium at some point.
Urea breath test
The H. pylori breath test is the most accurate noninvasive option. You breathe into a bag, swallow urea labelled with a special carbon atom, and breathe into a second bag about 15 minutes later; if H. pylori is present, the labelled carbon appears in your breath. In a Cochrane review of 101 studies (11,003 people), the carbon-13 breath test detected 94% of infections at a fixed specificity of 90%.
Stool antigen test
The H. pylori stool test looks for bacterial proteins (antigens) in a small stool sample you collect at home. It shows an active infection, before or after treatment; its sensitivity was 83% in the Cochrane analysis. It is not the same as a stool culture test, which looks for diarrhoea-causing bacteria. Stool PCR, offered by some labs, can also flag clarithromycin resistance.
Blood antibody test (serology)
A blood test measures antibodies. MedlinePlus explains that it is rarely used because it cannot tell a current infection from a past one, so it cannot check a cure. See our guide to serology tests.
Endoscopy with biopsy
During an upper endoscopy, a thin camera is passed into the stomach to take small tissue samples, examined under the microscope, on a rapid urease (CLO) test, by culture or by PCR. Culture and molecular tests show which antibiotics the bacterium resists. Endoscopy is the most accurate method and also shows ulcers or suspicious lesions.
| Test | Shows active infection? | Sensitivity (Cochrane, at 90% specificity) | Good for test of cure? |
|---|---|---|---|
| Urea breath test (carbon-13) | Yes | 94% | Yes |
| Urea breath test (carbon-14) | Yes | 92% | Yes |
| Stool antigen test | Yes | 83% | Yes |
| Blood antibodies (serology) | No: current or past | 84% | No |
| Endoscopy biopsy (histology, rapid urease, culture, PCR) | Yes | Reference standard | Yes, when an endoscopy is needed anyway |
How to prepare for an H. pylori test
To avoid falsely negative breath, stool or biopsy tests, the ACG advises:
- stop proton pump inhibitors (omeprazole, pantoprazole and others) 2 weeks before;
- stop antibiotics and bismuth products 4 weeks before;
- fast for a few hours before a breath test or an endoscopy, as your clinic instructs.
Ask your doctor before stopping any medicine. Results usually come back within one to three days.
How to read your H. pylori test results
A positive breath, stool or biopsy test means an active infection to treat. A negative result usually means no infection, unless you recently took the medicines above. A positive antibody test alone does not prove a current infection.
Blood tests often look for consequences of the infection. Usual adult values in traditional and SI units (UK labs report in SI units; ranges vary between labs):
| Test | Usual range (traditional units) | SI units | Why it matters with H. pylori |
|---|---|---|---|
| Haemoglobin | Men 13.8-17.2 g/dL; women 12.1-15.1 g/dL | Men 138-172 g/L; women 121-151 g/L | Low with anaemia from iron deficiency or a bleeding ulcer |
| Ferritin | Men 30-400 ng/mL; women 13-150 ng/mL | Men 30-400 µg/L; women 13-150 µg/L | Low with depleted iron stores; unexplained low iron is a reason to test |
| Platelet count | 150,000-400,000/µL | 150-400 × 10⁹/L | Low in ITP; below 50 × 10⁹/L raises bleeding risk |
| Vitamin B12 | 299-1,054 pg/mL | 219-773 pmol/L | Below 299 pg/mL (219 pmol/L) may mean deficiency, as in autoimmune gastritis |
If your complete blood count shows anaemia, an iron studies panel tells whether iron is the problem. Our guides to low ferritin, platelet count results and low vitamin B12 explain each value in detail.
H. pylori treatment: the 2024 ACG regimens
Everyone who tests positive should be treated, and antibiotic resistance drives the choice. A US meta-analysis (2011-2021) found resistance to metronidazole in 42.1% of strains, levofloxacin 37.6% and clarithromycin 31.5%, but only 2.6% for amoxicillin, 0.87% for tetracycline and 0.17% for rifabutin. Clarithromycin or levofloxacin regimens are used only when a test shows the strain is sensitive.
| Regimen (14 days) | Medicines | Place in the 2024 ACG guideline |
|---|---|---|
| Optimized bismuth quadruple therapy | PPI twice a day, bismuth 4 times a day, tetracycline 500 mg 4 times a day, metronidazole 500 mg 3-4 times a day | Preferred first treatment when resistance is unknown; preferred after a first failure |
| Rifabutin triple therapy | Rifabutin 50 mg, amoxicillin 1,000 mg and omeprazole 40 mg, 3 times a day | Alternative first treatment (no penicillin allergy); option after bismuth quadruple fails |
| Vonoprazan dual therapy | Vonoprazan 20 mg twice a day, amoxicillin 1,000 mg 3 times a day | Alternative first treatment (no penicillin allergy) |
| Vonoprazan triple therapy | Vonoprazan 20 mg, clarithromycin 500 mg, amoxicillin 1,000 mg, twice a day | Suggested when clarithromycin resistance is unlikely or excluded |
| Levofloxacin triple therapy | PPI and amoxicillin twice a day, levofloxacin 500 mg once a day | Only if the strain is shown to be sensitive |
Vonoprazan, a potassium-competitive acid blocker, suppresses acid more strongly and for longer than classic proton pump inhibitors, which helps the antibiotics work. If you are labelled allergic to penicillin, the ACG suggests referral for formal penicillin allergy testing, since amoxicillin is part of several regimens.
Side effects of H. pylori treatment
Most are mild and stop when the course ends. In the rifabutin trial, the most frequent were diarrhoea (12.7%), headache (11.9%) and discoloured urine (9.3%). Bismuth can darken the stool and tongue; MedlinePlus says this is harmless and fades within days, not to be confused with a black spot on the tongue or bleeding. Take every dose, even if you feel better.
The test of cure
Treatment can fail, so the ACG recommends a test of cure for everyone at least 4 weeks after treatment: breath test, stool antigen test or biopsy, with the same medicine pause as before, never a blood test. If H. pylori persists, a different regimen is chosen.
Can H. pylori be prevented?
There is no vaccine. MedlinePlus recommends handwashing, properly prepared food and safe drinking water. Testing adults who live with an infected person, as the ACG suggests, also limits spread within the family.
After a cure, reinfection is uncommon. A meta-analysis of 132 studies found a global annual recurrence rate of 4.3%, falling to 3.1% in countries with a very high human development index. Recurrence is higher in young children: 30% in children 5 or younger in a 2024 paediatric meta-analysis.
When to see a doctor
See your GP about H. pylori testing if you:
- have recurring burning upper belly pain, bloating or nausea;
- have had an ulcer, take NSAIDs or are starting daily aspirin;
- have unexplained iron deficiency or low platelets;
- live with someone who has H. pylori, or have a parent, sibling or child who had stomach cancer;
- still have symptoms after treatment, or never had a test of cure.
Call 999 for vomit with blood or that looks like coffee grounds, black tarry or bloody stools, sudden severe belly pain, fainting or a racing pulse: signs of a bleeding or perforated ulcer. Unintended weight loss, repeated vomiting or new iron deficiency need a prompt visit, because the ACG counts them as alarm features that call for an endoscopy.
Latest scientific advances in H. pylori
A new US guideline drops clarithromycin triple therapy as a default
The ACG guideline published in September 2024 recommends 14 days of bismuth quadruple therapy as the preferred first treatment when antibiotic resistance is unknown, with rifabutin triple therapy or vonoprazan dual therapy as alternatives. It also makes a test of cure universal. If you were treated in the past and never retested, ask for a breath or stool test.
Vonoprazan regimens beat older acid blockers
In the PHALCON-HP trial (1,046 adults in the US and Europe), eradication reached 80.8% with vonoprazan triple therapy and 77.2% with vonoprazan dual therapy, against 68.5% with lansoprazole triple therapy. In clarithromycin-resistant infections, the gap was large: 65.8% and 69.6% against 31.9%. The FDA approved the vonoprazan treatment packs in May 2022 (a US decision).
Treating H. pylori prevents stomach cancer
A 2025 meta-analysis of randomized trials found that eradication lowered gastric cancer risk by about a third in healthy infected people (relative risk 0.64) and gastric cancer deaths (0.78). In a Korean trial in relatives of gastric cancer patients, cancer developed in 1.2% of treated participants versus 2.7% with placebo over 9.2 years. The International Agency for Research on Cancer projects 15.6 million lifetime gastric cancers among people born in 2008-2017, 76% attributable to H. pylori.
Platelets rise after eradication in ITP
A 2026 meta-analysis of 8 randomized trials (297 patients with immune thrombocytopenia) found fewer non-responders after H. pylori eradication (risk ratio 0.65) and a larger rise in platelet count at about six months (about 62 × 10⁹/L more). The trials were small, so larger studies are needed.
Retesting at home
A University of Miami trial (NCT07224048), completed in April 2026, compared an at-home breath test with in-person retesting in 50 adults at least six weeks after treatment. Results are awaited; easier home testing could help more people confirm their cure.
Which tests can help?
Tests often ordered with an H. pylori workup:
- a urea breath test or stool antigen test to diagnose the infection, and again at least 4 weeks after treatment;
- a blood count, ferritin and iron studies for anaemia (see our guide to anaemia symptoms and blood tests);
- vitamin B12 if autoimmune gastritis is suspected;
- an endoscopy with biopsies, culture or PCR for alarm signs or after treatment failure.
Glossary
- Gastritis: inflammation of the stomach lining.
- Peptic ulcer: a sore in the lining of the stomach or the first part of the small intestine (duodenum).
- Urease: the H. pylori enzyme detected by the breath test and the rapid urease (CLO) test.
- PPI and potassium-competitive acid blocker: acid reducers such as omeprazole and vonoprazan.
- Bismuth quadruple therapy: a PPI, bismuth, tetracycline and metronidazole taken together for 14 days.
- Test of cure: a breath, stool or biopsy test at least 4 weeks after treatment to confirm the bacteria are gone.
- Immune thrombocytopenia (ITP): a low platelet count caused by the immune system.
Frequently asked questions
What is stomach H. pylori?
A bacterium living in the stomach lining that causes chronic gastritis. It infects about 44% of adults worldwide; most have no symptoms, but it can lead to ulcers and stomach cancer.
Can I kiss somebody if I have H. pylori?
Saliva is one possible route of spread, but most infections are caught in childhood. Rather than avoiding your partner, get treated and confirm the cure; adults in your household can be tested too, as the ACG suggests.
What are the potential side effects of H. pylori treatment?
Diarrhea, nausea, headache and, with bismuth, a dark tongue and dark stool. Rifabutin can discolour urine. These effects are usually mild and stop after the 14 days. Call your doctor for severe diarrhoea, and stop bismuth and call if you notice ringing in the ears.
What are the symptoms of H. pylori infection in children?
Most have none. When present: belly pain, nausea, vomiting and poor appetite. Unexplained iron deficiency can also be a clue.
Is H. pylori curable?
Yes. In trials of the recommended 14-day regimens, about 77% to 89% of people were cured by the first course; a different combination is used if it fails.
How do you remove H. pylori from the stomach?
With prescription antibiotics combined with a strong acid reducer and, often, bismuth, as in the regimens above; no home remedy is part of the guidelines. Probiotics may reduce side effects (risk ratio 0.54 in an umbrella review), but the evidence is weak.
Can H. pylori come back?
Rarely in adults: the annual recurrence rate is about 3% in high-income countries. A positive test of cure usually means the treatment failed rather than a new infection.
What are H. pylori cancer symptoms?
Early stomach cancer often has no symptoms. Warning signs include indigestion that does not go away, unintended weight loss, repeated vomiting, signs of bleeding such as black stool, and iron deficiency. See a doctor promptly if you notice any of them.
Sources
- Chey WD et al. — ACG Clinical Guideline: Treatment of Helicobacter pylori Infection — Am J Gastroenterol, 2024 — doi.org
- American College of Gastroenterology — ACG Guideline Highlights: Treatment of Helicobacter pylori Infection — ACG, 2025 — gi.org
- Malfertheiner P et al. — Management of Helicobacter pylori infection: the Maastricht VI/Florence consensus report — Gut, 2022 — doi.org
- Chen YC et al. — Global Prevalence of Helicobacter pylori Infection and Incidence of Gastric Cancer Between 1980 and 2022 — Gastroenterology, 2024 — doi.org
- Best LM et al. — Non-invasive diagnostic tests for Helicobacter pylori infection — Cochrane Database Syst Rev, 2018 — doi.org
- Ho JJC et al. — Helicobacter pylori Antibiotic Resistance in the United States Between 2011 and 2021: A Systematic Review and Meta-Analysis — Am J Gastroenterol, 2022 — doi.org
- Chey WD et al. — Vonoprazan Triple and Dual Therapy for Helicobacter pylori Infection in the United States and Europe: Randomized Clinical Trial — Gastroenterology, 2022 — doi.org
- Kalfus IN et al. — Rifabutin-Containing Triple Therapy (RHB-105) for Eradication of Helicobacter pylori: Randomized ERADICATE Hp Trial — Antibiotics, 2020 — doi.org
- Ford AC et al. — Eradication Therapy to Prevent Gastric Cancer in Helicobacter pylori-Positive Individuals: Systematic Review and Meta-Analysis — Gastroenterology, 2025 — doi.org
- Choi IJ et al. — Family History of Gastric Cancer and Helicobacter pylori Treatment — N Engl J Med, 2020 — doi.org
- Park JY et al. — Global lifetime estimates of expected and preventable gastric cancers across 185 countries — Nat Med, 2025 — doi.org
- Hudak L et al. — An updated systematic review and meta-analysis on the association between Helicobacter pylori infection and iron deficiency anaemia — Helicobacter, 2017 — doi.org
- Wang Z et al. — Impact of H. pylori infection on iron deficiency anaemia in children: a systematic review and meta-analysis — Front Microbiol, 2025 — doi.org
- Arnold DM et al. — Platelet count response to H. pylori treatment in patients with immune thrombocytopenic purpura with and without H. pylori infection: a systematic review — Haematologica, 2009 — doi.org
- Hattab M et al. — Helicobacter pylori eradication for immune thrombocytopenia reduces non-response and raises platelet counts: Meta-analysis of randomized trials — Ann Hematol, 2026 — doi.org
- Li M et al. — Prevalence of Autoimmune Gastritis Worldwide: A Systematic Review and Meta-Analysis — Helicobacter, 2025 — doi.org
- Hu Y et al. — Systematic review with meta-analysis: the global recurrence rate of Helicobacter pylori — Aliment Pharmacol Ther, 2017 — doi.org
- Xu L et al. — Global H. pylori recurrence, recrudescence, and re-infection status after successful eradication in paediatric patients — J Gastroenterol, 2024 — doi.org
- Linh TD et al. — Prevalence of H. pylori Infection in Children From Households With Members' History of Successful Eradication — JGH Open, 2026 — doi.org
- Yang Z et al. — The effects of probiotics supplementation on Helicobacter pylori standard treatment: an umbrella review — Sci Rep, 2024 — doi.org
- Shakir SM et al. — Updates to the Diagnosis and Clinical Management of Helicobacter pylori Infections — Clin Chem, 2023 — doi.org
- University of Miami — Helicobacter Pylori Screening and Treatment in the At-risk South Florida Community-AIM 2 (NCT07224048) — ClinicalTrials.gov — clinicaltrials.gov
- US Food and Drug Administration — Drugs@FDA: Voquezna Triple Pak (NDA 215152) — FDA, 2022 — fda.gov
- National Cancer Institute — Helicobacter pylori and Cancer — NCI — cancer.gov
- National Institute of Diabetes and Digestive and Kidney Diseases — Symptoms and Causes of Peptic Ulcers — NIDDK — niddk.nih.gov
- MedlinePlus — Helicobacter Pylori Infections — National Library of Medicine — medlineplus.gov
- MedlinePlus — Helicobacter pylori (H. pylori) Tests — National Library of Medicine — medlineplus.gov
- MedlinePlus — Bismuth Subsalicylate — Drug information — medlineplus.gov
- MedlinePlus — Haemoglobin, Ferritin, Platelet count and Vitamin B12 level tests — Medical Encyclopedia — medlineplus.gov
- Cleveland Clinic — H. Pylori Infection — Cleveland Clinic — clevelandclinic.org
- Cleveland Clinic — H. Pylori Tests — Cleveland Clinic — clevelandclinic.org
- NHS — Stomach ulcer (H. pylori infection) — National Health Service (England) — nhs.uk
Further reading
- H. pylori test: what the colon cancer link means
- Stomach cancer: symptoms, causes and treatment
- Anaemia: symptoms, causes and blood tests
- Ferritin blood test: levels and what they mean
- Vitamin B12 blood test: how to read results
- Black specks in stool: causes, tests and red flags
- Gluten intolerance vs celiac disease
Understand your lab results with AI DiagMe
An H. pylori workup often comes with several reports: a breath or stool test, a blood count, ferritin and iron studies, sometimes vitamin B12. AI DiagMe reads your lab report in minutes, explains each result in plain language, shows what needs follow-up and suggests questions to ask your doctor. Upload your lab results to AI DiagMe for a clear, personal report.
