Everything You Need to Know About H. pylori — The Infection That Affects Far More Than Your Stomach
WELYON · The Root Cause Investigation welyon.com
DIGITAL GUIDE NO. 9
The Root Cause
Investigation
Everything You Need to Know About H. pylori — The Infection That Affects Far More Than Your Stomach
Start here. Find your condition. Take the test.
April 2026 · © Welyon. All rights reserved.
HOW TO USE THIS GUIDE
This is the starting point guide in the Welyon series. It gives you the overview — what H. pylori is, why it matters far beyond the stomach, and which conditions are associated with it in the peer-reviewed literature.
If you recognise a condition in this guide, there is a dedicated investigation guide for it. Each condition guide contains the full evidence picture, the mechanisms, the diagnostic steps, and what to bring to a physician. This guide tells you where to go — the condition guides tell you what to do when you get there.
SECTION 01 WHAT H. PYLORI IS — AND WHY ALMOST NOBODY KNOWS ENOUGH ABOUT IT
The Basics
Helicobacter pylori is a bacterium that lives in the stomach. It is classified by the World Health Organization as a Group 1 carcinogen — meaning there is sufficient evidence that it causes cancer in humans, specifically gastric cancer and a type of stomach lymphoma called MALT lymphoma. It is also the primary cause of peptic ulcers.
Most people who know about H. pylori stop there — stomach ulcers, stomach cancer, a stomach bug. The much larger and less well-known part of the story is that H. pylori is a systemic infection whose effects extend far beyond the stomach, through mechanisms that are documented in the peer-reviewed medical literature and that are almost never investigated in the clinical settings where affected patients are actually seen.
How Common Is It?
Approximately one in three Americans carries H. pylori. Globally, it colonises an estimated 4.4 billion people. The infection is typically acquired in childhood. It persists indefinitely without treatment. Most carriers have no stomach symptoms — no ulcers, no obvious pain, no warning signs.
The majority of people carrying H. pylori are completely unaware of it. And in a meaningful proportion of those people, the infection is quietly contributing to health conditions that are being managed in entirely different medical specialties, without anyone connecting them to the stomach.
1 in 3 Americans carries H. pylori — most with no stomach symptoms and no awareness of the infection |
What H. pylori Does in the Body
H. pylori does not simply sit in the stomach passively. It actively defends itself and actively affects the body through several documented mechanisms:
It produces an alkaline shield using urease, protecting itself from stomach acid
It constructs a biofilm that makes it harder for antibiotics and immune cells to reach it
It generates chronic low-grade systemic inflammation through proteins that enter the bloodstream and circulate throughout the body
In some people, it generates antibodies through molecular mimicry — where the immune system’s response to H. pylori also attacks the body’s own tissues
These mechanisms explain why H. pylori’s effects extend so far beyond the stomach. The bacterium stays in the stomach, but its effects travel. Iron deficiency, B12 depletion, autoimmune activation, and cognitive effects are all documented consequences of the same infection.
SECTION 02 THE CONDITIONS — WHAT H. PYLORI IS ASSOCIATED WITH
The following conditions have documented associations with H. pylori in the peer-reviewed literature. The evidence strength varies considerably — from strong and guideline-endorsed for some conditions, to moderate and emerging for others. This guide is honest about those differences.
| Guide | Condition | Evidence | The question this raises |
| G1 | Chronic Fatigue | MODERATE | Why am I this tired when nothing shows up on my tests? |
| G2 | Brain Fog / Cognitive Symptoms | MODERATE | Why am I being told my labs are normal when I can feel something is wrong? |
| G3 | Iron Deficiency / Refractory IDA | STRONG | Why won’t my iron respond to supplements? |
| G4 | Thyroid Autoimmunity (Hashimoto’s / Graves’) | MODERATE | What might have triggered my immune system to attack my thyroid? |
| G5 | Metabolic Syndrome / Insulin Resistance | EXPLORATORY | Is something interfering with my metabolism at the biochemical level? |
| G6 | Nerve & Energy (B12 / gut-brain axis) | MODERATE | What is the mechanism connecting my gut to my nerves and cognition? |
| G7 | Skin / Chronic Hives (urticaria, rosacea) | MODERATE | Why do antihistamines manage my hives but never resolve them? |
| G8 | Immune / ITP & Autoimmunity | STRONG | Could one infection be driving multiple autoimmune conditions simultaneously? |
WHAT ‘EVIDENCE STRENGTH’ MEANS IN THIS CONTEXT STRONG means the association is supported by multiple randomised controlled trials or meta-analyses with consistent results. For some conditions, H. pylori testing is guideline-endorsed. MODERATE means the association is consistent across studies, mechanistically plausible, and supported by some interventional evidence — but not yet at the level of strong RCT data. Investigating H. pylori is warranted; guaranteeing improvement is not. EXPLORATORY means the association is biologically plausible and supported by early evidence — observational signals, small studies, or mechanism — but not yet by consistent interventional data. The association may be real; the clinical benefit of eradication is not yet reliably demonstrated. Worth investigating; not established. In every case: H. pylori testing is inexpensive, non-invasive, and available without a physician order. The cost of not asking the question is always higher than the cost of the test. |
SECTION 03 THE DIAGNOSIS GAP — WHY NOBODY TOLD YOU ABOUT THIS
The Specialty Problem
H. pylori is managed by gastroenterologists. The conditions listed above are managed by haematologists, endocrinologists, dermatologists, allergists, neurologists, and primary care physicians. These specialties have different training, different clinical algorithms, and different diagnostic frameworks. No standard clinical algorithm connects a gastric infection to refractory iron deficiency, thyroid autoimmunity, chronic urticaria, or cognitive symptoms in non-gastroenterology settings.
The connection is in the research literature — in gastroenterology journals, immunology journals, and haematology journals. It is not in the clinical decision trees that most physicians use when seeing patients with these conditions. The gap is structural.
The Scale of What Is Being Missed
Conservative modelled estimates suggest that between 5–15 million Americans in the higher-evidence categories alone — iron deficiency anaemia, B12 deficiency, chronic urticaria, and ITP — may be living with an H. pylori infection that has never been investigated as a contributor to their condition. When broader associated conditions are included, the potential untested population expands to an estimated 20–35 million U.S. adults.
20–35 million U.S. adults may have at least one H. pylori-associated systemic condition while remaining untested for the infection |
A Structural Gap — Not a Failure of Individual Physicians
The specialists managing these conditions are doing appropriate, evidence-based work within the framework of their specialty. Haematologists treating ITP, endocrinologists prescribing levothyroxine, dermatologists prescribing antihistamines — all of these are appropriate responses to the conditions as they present. What is missing is the upstream investigation that lies in a no-man’s-land between specialties. The research exists. The test exists. The treatment exists. A systematic clinical pathway connecting them does not yet exist at scale.
SECTION 04 STANDARD TREATMENT — WHAT EXISTS
What Standard Eradication Looks Like
When H. pylori is diagnosed and treated, the standard approach is a course of antibiotics combined with acid suppression. The 2024 American College of Gastroenterology guideline recommends bismuth quadruple therapy as the preferred first-line treatment — a 14-day course combining bismuth subcitrate, a proton pump inhibitor, tetracycline, and metronidazole. This regimen achieves eradication in approximately 84–87% of patients who start treatment, and 95–96% of those who complete the full course correctly.
AN IMPORTANT CAVEAT ON THE MOST COMMONLY PRESCRIBED REGIMEN The most commonly prescribed H. pylori treatment in the United States is clarithromycin triple therapy. The 2024 ACG guideline formally deprecated this regimen as a first-line option because clarithromycin resistance rates in the United States now exceed 30% in many regions. Despite this guideline update, more than half of U.S. H. pylori patients continue to receive it. If your physician prescribes this regimen, it is appropriate to ask specifically about bismuth quadruple therapy. If eradication fails, do not repeat the same regimen. |
Each condition guide in the Welyon series explains what confirmed eradication looks like for that condition — what markers to track, what timeline to expect, and what to discuss with a physician after treatment.
SECTION 05 YOUR NEXT STEPS
Step 1 — Identify your condition
Review the conditions table in Section 02. If one or more conditions resonate with your health history, that is your starting point. Each condition has a dedicated Welyon guide with the full evidence picture and investigation plan. This overview tells you the map. The condition guides give you the directions.
Step 2 — Test
The H. pylori stool antigen test is accurate (over 90% sensitivity and specificity), non-invasive, and available at-home without a physician order. The urea breath test, available at most clinical labs, is equally accurate.
Do not use a blood antibody test for initial diagnosis — it detects past exposure, not active infection
Hold proton pump inhibitors (PPIs) for at least 2 weeks before testing — they suppress H. pylori and cause false negatives
Hold antibiotics for 4 weeks before testing for the same reason
Step 3 — Pursue eradication if positive
Consult a physician about bismuth quadruple therapy — the 2024 ACG guideline’s preferred first-line regimen
Complete the full course — the compliance gap between per-protocol and intention-to-treat eradication rates is almost entirely a completion problem
Confirm eradication at 4 weeks with a stool antigen or breath test — not a blood test
Track your condition-specific markers at 3 and 6 months — systemic effects resolve on a biological timeline, not within days of completing treatment
If you want a self-directed supplement regimen built on the same evidence architecture, the HP Stack DIY Guide is available now at welyon.com. The HP Stack supplement and a physician-supervised HP Program are both in development.
THE WELYON GUIDE SERIES
| 1 | Fatigue That Sleep Doesn’t Fix | For unexplained fatigue and energy depletion |
| 2 | The Brain Fog Investigation | For cognitive symptoms and unexplained mental fatigue |
| 3 | Why Your Iron Won’t Budge | For refractory iron deficiency and IDA |
| 4 | The Thyroid-Stomach Connection | For Hashimoto’s and Graves’ disease |
| 5 | The Metabolic Missing Link | For insulin resistance and metabolic syndrome |
| 6 | Your Gut Is Talking to Your Brain | For nerve & energy, B12, and the gut-brain axis |
| 7 | Skin From the Inside Out | For chronic urticaria and rosacea |
| 8 | Your Immune System Is Confused | For ITP and multiple autoimmune conditions |
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REFERENCES AND ENDNOTES
Key references supporting the overview claims in this guide. Full citations for condition-specific claims are in each condition’s dedicated guide.
1. Hooi JKY, et al. Global Prevalence of Helicobacter pylori Infection: Systematic Review and Meta-Analysis. Gastroenterology. 2017;153(2):420-429.
2. Shah SC, et al. Helicobacter pylori Burden in the United States According to Individual Demographics and Geography: A Nationwide Analysis of the Veterans Healthcare System. Clin Gastroenterol Hepatol. 2023;22(1):42-50.e26.
3. Chey WD, et al. 2024 American College of Gastroenterology Clinical Guideline: Treatment of Helicobacter pylori Infection. Am J Gastroenterol. 2024.
4. Ho JJC, et al. Helicobacter pylori antibiotic resistance in the United States 2011–2021. Am J Gastroenterol. 2022;117(8):1221-1230.
5. Chey WD, Megraud F, Laine L, et al. Vonoprazan Triple and Dual Therapy for H. pylori. Gastroenterology. 2022;163(3):608-619.
6. Hudak L, et al. Updated systematic review and meta-analysis on the association between H. pylori infection and iron deficiency anemia. Helicobacter. 2017;22(1):e12330.
7. Hou Y, et al. Meta-analysis of the correlation between H. pylori infection and autoimmune thyroid diseases. Oncotarget. 2017;8(70):115691-115700.
8. Watanabe J, et al. Effects of Antibiotics for H. pylori Eradication on Chronic Spontaneous Urticaria. Antibiotics. 2021;10(2):156.
9. Vishnu P, et al. International survey on Helicobacter pylori testing in patients with immune thrombocytopenia. J Thromb Haemost. 2021;19(1):287-296.
10. Wang K, et al. Bidirectional Mendelian randomization — H. pylori and autoimmune thyroid disease. Sci Adv. 2024;10(31):eadi8646.