Helicobacter pylori (H. pylori): symptoms, testing and treatment

H. pylori is a group of bacteria that live in the sticky mucus that lines the stomach. Guts UK says up to 2 in 5 people in the UK have H. pylori in their stomach, and that it does not cause any problems for 8 to 9 out of 10 people.

H. pylori are spiral-shaped bacteria that live in the sticky mucus lining the stomach. Guts UK explains that the infection always causes some inflammation of the stomach lining, usually starting in the lower part of the stomach, the antrum, and sometimes spreading to the whole stomach. For most people this inflammation causes no symptoms and is never noticed.

Because of what it can lead to in a minority of people (gastritis, peptic ulcers and, very rarely after decades, stomach cancer), Guts UK says that where H. pylori is found it should always be treated to reduce the risk of complications.

Guts UK lists belly pain (often a gnawing ache), feeling sick, belly bloating and burping as symptoms of H. pylori gastritis, noting that not all might be present. Indigestion is the symptom most associated with the infection, but Guts UK stresses that in the majority of people with indigestion the cause is something else, most commonly functional dyspepsia, and that people can have both without one causing the other.

Ulcers are the best-known complication. The NHS says the main symptom of a stomach ulcer is tummy pain that is usually in the upper tummy, may feel like burning and is often worse at night, along with indigestion, heartburn, bloating and feeling or being sick. Guts UK says about 3 in 20 people with H. pylori have ulcers, and that ulcers occasionally bleed or perforate.

Guts UK says a very small number of people with long-standing, untreated infection may develop stomach cancer, after decades, with between 1 and 3 people out of 100 affected. Cancer Research UK lists H. pylori infection among the factors that increase the risk of stomach cancer. Symptoms that raise suspicion include being sick, unintentional weight loss, difficulty or pain on swallowing and a low iron level in the blood, which need urgent assessment.

• Urgent GP appointment or NHS 111 (NHS, for a suspected stomach ulcer): tummy pain that is getting worse or does not go away, loss of appetite, feeling full after a very small amount of food, losing weight without trying, a lump in the tummy, painful or difficult swallowing, keeping being sick, or feeling tired all the time.

• 999 or A&E (NHS): vomiting bright red blood or vomit that looks like ground coffee, blood in your poo or poo that is black, sticky and very smelly, severe tummy pain, a tummy that is painful to touch, or sudden chest pain.

Guts UK says it is not completely clear how H. pylori passes from one person to another, but a faeco-oral route is usually proposed, in which bacteria in poo move from one person to another person's mouth. It is also unclear why only some people with the infection go on to develop symptoms or complications such as ulcers.

Guts UK says people who have H. pylori almost always catch it in childhood, when the immune system is not yet mature enough to repel the infection, and that transmission usually occurs within families, mostly from parents to children. It stays in the stomach unless it is treated with specific antibiotics. The infection is becoming less common in the UK, acquiring it as an adult is very rare, and once it has been treated and cured, getting infected again is very unusual.

It happens more often in people with learning disabilities, where Guts UK says it can be present in 9 out of 10 people.

Guts UK and NHS inform describe the same main options. A urea breath test involves drinking a solution containing urea and giving breath samples before and after; H. pylori break the urea down and the change is detected. A stool antigen test looks for bacterial proteins in a small stool sample and Guts UK says it is as accurate as the breath test. Blood antibody tests have largely been replaced, according to NHS inform.

An endoscopy (gastroscopy) lets a doctor look at the stomach and take a small biopsy that can be tested for the bacteria. Guts UK says that in people with indigestion and no alarm features, doctors now usually test for H. pylori first rather than going straight to endoscopy, but that anyone with unintentional weight loss, persistent vomiting or swallowing difficulty still needs endoscopy.

Results can be misleading if you have taken certain medicines. NICE CKS and Guts UK say that tests should not be done if you have taken antibiotics in the past 4 weeks or a proton pump inhibitor in the last 2 weeks. Tell the person arranging the test what you take, and do not stop prescribed medicines without asking.

Guts UK says treatment consists of a combination of 3 to 4 different tablets, one to cut down the amount of acid in the stomach and the others antibiotics, and it is the combination that matters. One-week triple therapy was traditionally used, but 2-week triple therapy is now recognised as more effective. A newer medication containing two antibiotics and bismuth is available in the UK, and 10 days of it alongside an acid-reducing medicine is also a useful regimen.

NHS inform lists amoxicillin, clarithromycin and metronidazole among the antibiotics used. Most people have no side effects, but Guts UK says some notice a strange taste in the mouth, a feeling of sickness or a headache, and that with metronidazole you should avoid alcohol. Treatment is much more successful if the whole course is taken exactly as prescribed.

Treatment does not always clear the bacteria, so your doctor should check afterwards. Guts UK says the breath test needs to be done at least one month after treatment, and that if the result is still positive further treatment is possible. NICE CKS says routine re-testing is not offered in every case but may be considered in some circumstances, with second-line treatment offered if it is positive, so ask your clinician what is planned.

The NHS says treatment for a stomach ulcer usually lasts from 1 week to 2 months depending on the cause, and that you may need tests after treatment to make sure it has worked. If symptoms come back, speak to a GP.

Guts UK says treatment is usually very successful, although symptoms may take a little time to settle, and that if symptoms were due to an ulcer, most people recover without further complications. If there was no ulcer, some people see a significant reduction in symptoms and others do not, in which case other causes such as functional dyspepsia should be discussed. It says benefit may not be seen for 12 months.

Guts UK recommends testing for H. pylori in first-degree relatives of people with stomach cancer, which is something to raise with a GP if it applies to you. Clearing the bacteria greatly reduces the chance of ulcers coming back, because ulcers that once healed with acid-reducing medicine alone tended to return when treatment stopped.

On the NHS, testing is usually arranged by a GP, either because of dyspepsia, ulcers or a history of stomach cancer in the family, with a breath or stool test and a prescription for eradication therapy. Endoscopy is arranged by hospital teams where alarm symptoms are present or treatment has failed.

Private H. pylori breath and stool tests are widely offered, and some people use them for peace of mind or speed. Whichever route you take, it is important that the test is done off acid-suppressing medicines and antibiotics for the periods stated above, that a positive result leads to treatment under a prescriber who knows your medical history and allergies, and that clearance is checked afterwards.