Gastritis is inflammation of the stomach lining. It can come on suddenly and last a few days, or it can develop slowly over months or years. Most people with gastritis don’t actually have symptoms, but when they do, the most common complaint is pain or discomfort in the upper abdomen. The condition ranges from mild irritation that resolves on its own to chronic inflammation that, left untreated, can lead to ulcers or raise the risk of stomach cancer.
How the Stomach Lining Gets Damaged
Your stomach lining produces a thick layer of mucus that protects it from its own digestive acid. Gastritis develops when something disrupts that protective barrier, allowing acid to irritate or erode the tissue underneath. Depending on the cause, this can happen through reduced mucus production, physical disruption of the barrier, or decreased blood flow to the lining itself.
Once the barrier is compromised, immune cells rush to the damaged area. In acute gastritis, these are mainly fast-acting inflammatory cells called neutrophils. In chronic gastritis, the immune response shifts to longer-term players, and the ongoing inflammation can gradually thin the stomach lining over time.
The Most Common Causes
A bacterial infection called H. pylori is the leading cause of chronic gastritis worldwide. The bacterium survives the stomach’s harsh acid by producing an enzyme that neutralizes acid in its immediate surroundings. It then uses whip-like tails to swim through the mucus layer and attaches directly to the cells lining the stomach wall. Once anchored, H. pylori injects proteins into those cells that hijack their normal signaling, trigger persistent inflammation, and help the infection evade the immune system. The result is a cycle of chronic irritation that can last years if untreated.
Pain relievers like ibuprofen, aspirin, and naproxen are the other major culprit. These drugs work by blocking enzymes involved in inflammation throughout the body, but those same enzymes also help maintain the stomach’s protective mucus layer. Without adequate mucus, the stomach wall becomes vulnerable. These medications also increase stomach muscle contractions at higher doses, which compresses blood vessels in the stomach wall and reduces blood flow to the lining, compounding the damage.
Other causes include heavy alcohol use, severe physical stress (such as major surgery, burns, or critical illness), and autoimmune conditions where the immune system attacks the stomach lining directly.
Acute vs. Chronic Gastritis
Acute gastritis appears suddenly and typically resolves within days to weeks once the trigger is removed. It’s often caused by a bout of heavy drinking, a short course of pain relievers, or a sudden infection. The inflammation tends to be superficial.
Chronic gastritis develops gradually and persists for months or years. H. pylori infection is the most common driver. Over time, the ongoing inflammation can cause the stomach lining to thin and lose the specialized cells that produce acid and digestive enzymes. This process, called atrophy, is what links chronic gastritis to more serious complications down the line.
Symptoms to Recognize
Many people with gastritis feel nothing at all. When symptoms do appear, they typically include:
- Pain or a burning sensation in the upper abdomen
- Nausea or vomiting
- Feeling full unusually early during a meal
- Bloating or uncomfortable fullness after eating
- Loss of appetite
- Unintentional weight loss
If the inflammation progresses to erosions or ulcers, the stomach lining can bleed. Signs of bleeding include black or tarry stools, vomit that looks like coffee grounds, and feeling lightheaded, tired, or short of breath. Small amounts of bleeding may go unnoticed entirely, only showing up on a lab test that checks for hidden blood in the stool.
How Gastritis Is Diagnosed
An upper endoscopy with biopsy is the gold standard for diagnosing gastritis. During this procedure, a thin flexible tube with a camera is passed through the mouth into the stomach, allowing a doctor to visually inspect the lining and take small tissue samples. Under a microscope, pathologists look for specific markers: the type and density of immune cells present, whether the inflammation is active or chronic, signs of thinning in the stomach lining, and the presence or absence of H. pylori bacteria on the tissue surface.
The severity of an H. pylori infection is graded by how much of the stomach surface the bacteria cover, from scattered organisms on less than a third of the lining to dense layers across two-thirds or more. Biopsies are typically taken from the lower portion of the stomach, which is the most reliable site for detecting the infection.
Autoimmune Gastritis and B12 Deficiency
Autoimmune gastritis is a distinct form where the immune system specifically attacks the acid-producing cells in the upper part of the stomach. These cells do two critical jobs: they secrete stomach acid and they produce a protein called intrinsic factor, which your body needs to absorb vitamin B12 from food.
As the immune attack destroys these cells over time, two things happen. First, the stomach loses its ability to produce acid, which is itself needed to release B12 from food. Second, without intrinsic factor, even the B12 that does get released can’t be absorbed in the intestine. This double hit makes vitamin B12 deficiency, known as pernicious anemia, one of the hallmark consequences of autoimmune gastritis. Symptoms of B12 deficiency include fatigue, numbness or tingling in the hands and feet, difficulty with balance, and cognitive changes.
What Happens If Gastritis Goes Untreated
Acute gastritis that resolves on its own rarely causes lasting damage. Chronic gastritis is the concern. Persistent H. pylori infection can progress from chronic inflammation to stomach ulcers, and in some people, the ongoing damage leads to increasingly severe changes in the stomach lining. The National Cancer Institute identifies chronic atrophic gastritis as a risk factor for stomach cancer and a type of lymphoma that develops in the stomach’s immune tissue. Not everyone with chronic gastritis develops these complications, but eradicating H. pylori infection when it’s present significantly reduces the risk.
Treatment and Healing
Treatment depends on the cause. For H. pylori infection, the standard approach combines acid-reducing medication with antibiotics to eliminate the bacteria. For gastritis caused by pain relievers, stopping or reducing the offending medication is the first step.
Acid-reducing medications called proton pump inhibitors (PPIs) are the cornerstone of treatment across most forms of gastritis. These drugs block the stomach’s acid-producing pumps, raising the stomach’s pH and giving the inflamed lining a chance to heal. They vary in potency, and splitting a dose into twice daily is often more effective at controlling acid than taking a larger single dose. The duration of treatment depends on the severity and underlying cause, ranging from a few weeks for mild cases to several months for significant erosion or ulceration.
For autoimmune gastritis, there is no way to stop the immune attack on stomach cells, so management focuses on monitoring for complications and supplementing vitamin B12, typically through injections that bypass the need for intestinal absorption.
Foods and Habits That Make It Worse
While dietary changes alone won’t cure gastritis, avoiding certain triggers can reduce discomfort significantly while the stomach heals. The main offenders are spicy foods, alcohol, coffee and other caffeinated drinks, carbonated beverages, and fried or high-fat foods. All of these either stimulate acid production, irritate the already inflamed lining, or both.
If coffee is part of your daily routine, cutting back gradually helps avoid caffeine withdrawal headaches on top of stomach trouble. Eating smaller, more frequent meals rather than large ones can also ease symptoms by reducing the amount of acid your stomach produces at any given time.