What gastritis is and what causes it
Gastritis is the medical term for inflammation of the stomach lining. It's extremely common, and for most people it's a short-lived, manageable condition rather than a serious one. It can be acute (coming on suddenly, sometimes within hours of a trigger such as a heavy drinking session or a course of NSAID painkillers, and settling within days) or chronic (lingering for weeks, months or longer if the underlying trigger isn't identified and addressed).
The single most common cause is infection with Helicobacter pylori (H. pylori), a bacterium that many people carry in their stomach, often without knowing it, sometimes for years before it causes any problems. Beyond infection, gastritis is also commonly triggered by regular use of non-steroidal anti-inflammatory painkillers such as ibuprofen or aspirin, heavy or long-term alcohol use, smoking, and severe physical stress such as major surgery, serious illness, burns or injury, which can cause what's sometimes called stress gastritis in hospital settings. A less common cause is the immune system mistakenly attacking the cells of the stomach lining, known as autoimmune gastritis, which can affect the body's ability to absorb vitamin B12 and iron over time.
Reflux of bile from the small intestine back into the stomach can also irritate the lining and contribute to symptoms, as can repeated vomiting from another cause. It's worth saying that gastritis isn't caused by stress or spicy food alone, though both can make existing symptoms feel worse once inflammation is already present, and it isn't typically caught from another person or from a pet.
Symptoms of gastritis
Some people with gastritis, particularly when it's caused by H. pylori, have no symptoms at all and only find out incidentally during an unrelated test. When symptoms do occur, the most commonly reported are:
- Tummy pain or a burning, gnawing discomfort in the upper abdomen
- Indigestion that doesn't settle with over-the-counter remedies
- Bloating and a feeling of fullness after only a small meal
- Nausea, and sometimes vomiting
- Reduced appetite
- Excessive burping or wind
These symptoms overlap considerably with other digestive conditions such as acid reflux, IBS and ordinary indigestion, so symptoms alone can't confirm gastritis. If indigestion-type symptoms last longer than a week, keep coming back, or get worse, it's reasonable to see a GP rather than keep self-treating.
Symptoms also don't always reflect how inflamed the stomach lining actually is: some people with quite marked inflammation on endoscopy report only mild discomfort, while others with milder inflammation feel it more intensely. This is one reason clinicians rely on testing for the underlying cause rather than judging severity from symptoms alone.
How gastritis is diagnosed
A GP will usually start by asking about your symptoms, any regular medicines (particularly NSAID painkillers), alcohol intake and smoking, since these point towards the likely cause. Because H. pylori is the most common trigger, testing for it is often the first step: either a breath test, where you swallow a small amount of labelled urea and breathe into a collection device, or a stool sample test that checks for the bacterium's proteins. Both are straightforward and don't require sedation.
A blood test can sometimes be used, though it mainly shows whether you've ever been exposed to H. pylori rather than confirming a current, active infection, so it's less useful for diagnosis on its own. If your symptoms are severe, don't improve with initial treatment, or if you have any red-flag symptoms (covered below), your GP may refer you for an endoscopy, where a thin camera is passed into the stomach to look at the lining directly and take a small sample if needed.
Testing accuracy can be affected by recent medicines: proton pump inhibitors and antibiotics can temporarily suppress H. pylori enough to produce a false negative result, so your GP may ask you to pause certain medicines for a set period before a breath or stool test. It's worth mentioning any current medicines, including over-the-counter antacids, when you book a test so timing can be planned properly.
You generally don't need to fast or prepare for the initial GP assessment itself, though you may be asked not to eat or drink for a short period directly before a breath test. If you're referred for an endoscopy, you'll usually be asked to fast for several hours beforehand and given separate written instructions, since it's a more involved procedure than a simple breath or stool sample.
How gastritis is treated
Treatment depends entirely on the underlying cause rather than following a single fixed approach. If H. pylori is confirmed, the standard NHS treatment is a short course of antibiotics combined with a medicine that reduces stomach acid, which together clear the infection and let the stomach lining heal. If you'd like more detail on exactly how this works, our separate article on H. pylori infection, testing and treatment covers the antibiotic regimens in full.
Where gastritis isn't caused by infection, or alongside H. pylori treatment, medicines that reduce stomach acid are commonly used to ease symptoms and give the lining time to repair. These include proton pump inhibitors such as omeprazole or lansoprazole, H2-receptor blockers such as famotidine, or simple antacids for milder, occasional symptoms. Our guide to omeprazole vs lansoprazole explains how the two most commonly prescribed PPIs compare.
Alongside any medicine, addressing the trigger matters just as much: switching away from regular ibuprofen or aspirin where your GP agrees it's safe to do so, cutting back on alcohol, and stopping smoking all help the stomach lining recover and reduce the chance of symptoms returning. Most people notice an improvement within a few days to a couple of weeks of starting appropriate treatment, though full healing of the lining can take longer.
Autoimmune gastritis is managed slightly differently, since there's no infection to clear: treatment focuses on monitoring and correcting any resulting vitamin B12 or iron deficiency, alongside regular review, as the inflammation itself can't be reversed with antibiotics or acid-suppressing medicines.
Gastritis vs stomach ulcer: what is the difference
Gastritis and a stomach (peptic) ulcer are closely related but not the same thing. Gastritis is inflammation of the stomach lining; a stomach ulcer is an actual break or sore in that lining, which can develop if inflammation is left untreated for long enough. In practice, the two share many of the same underlying causes, chiefly H. pylori infection and regular NSAID use, and often produce similar symptoms, which is why they're frequently investigated and treated together.
The main practical difference is risk: an ulcer carries a higher chance of complications such as bleeding or, rarely, a perforation (a hole forming in the stomach wall), which is why the red-flag symptoms below matter whether you've been told you have gastritis, an ulcer, or simply haven't been tested yet. Both conditions are diagnosed with the same tests, H. pylori breath or stool testing and, where needed, endoscopy, and both generally improve with the same combination of treating the underlying cause and reducing stomach acid while the lining heals.
Not everyone with gastritis goes on to develop an ulcer, and plenty of people have gastritis for a time without ever progressing to one, particularly when the cause is identified and treated promptly. The risk rises mainly with how long the inflammation goes untreated and with ongoing exposure to the same triggers, which is part of why GPs tend to investigate and treat the underlying cause rather than only prescribing something to settle symptoms.
When to see a doctor
Most gastritis is manageable with GP-guided treatment and isn't a medical emergency. However, certain symptoms need same-day assessment, because they can signal a bleeding or perforated ulcer or another serious problem:
- Vomiting blood, or vomit that looks like coffee grounds
- Black, tarry or very dark stools
- Sudden, severe tummy or chest pain
Call 999 or go to A&E for any of these, or ask someone to drive you rather than driving yourself. Separately, get an urgent GP appointment or call NHS 111 if you've lost your appetite, have lost weight without trying, feel a lump in your tummy, find swallowing painful or difficult, or keep being sick. Outside of these red flags, book a routine GP appointment if indigestion-type symptoms last longer than a week, get worse, or keep coming back, so the underlying cause can be identified and treated properly rather than managed with over-the-counter remedies alone.