The most common reason to kill bacteria in your stomach is an infection with H. pylori, a spiral-shaped bacterium that burrows into the stomach lining and can cause ulcers, chronic gastritis, and increased cancer risk. Your stomach already kills most bacteria on its own, maintaining an acid pH around 2.0, but H. pylori has evolved a remarkable trick: it produces ammonia to neutralize the acid in its immediate surroundings, keeping its own environment at a comfortable pH of about 6.1 even when surrounded by harsh gastric acid. That’s why eliminating it requires a targeted approach combining prescription medications, and sometimes dietary support.
How Your Stomach Already Fights Bacteria
Gastric acid is your first line of defense. At a pH of roughly 2.0, the stomach’s acid bath destroys the vast majority of bacteria you swallow with food and water. Most pathogens simply can’t survive this environment long enough to cause trouble. This is why food poisoning typically involves bacteria that either overwhelm the system in sheer numbers or produce toxins before they’re killed.
H. pylori is the notable exception. It doesn’t live in the acid itself but in the mucus layer coating the stomach wall, where the pH ranges from 4.5 to 6.5. It also produces an enzyme called urease that generates ammonia and carbon dioxide, effectively building a chemical shield against acid. This is why no amount of dietary acid, lemon juice, or vinegar will clear an H. pylori infection. The bacterium has been co-evolving with human stomachs for tens of thousands of years.
First, Confirm the Infection
Before starting any treatment, you need to know what you’re dealing with. Several tests can detect H. pylori, and they vary significantly in reliability. A stool antigen test has a sensitivity of about 93% and specificity of about 93%, making it a solid noninvasive option. Blood antibody tests are less reliable, averaging around 78% accuracy, and they can’t distinguish between a current and past infection.
The urea breath test is the gold standard among noninvasive options. You drink a solution containing labeled carbon, and if H. pylori is present, its urease enzyme breaks down the compound in a way that’s detectable in your breath. When performed during endoscopy, this test reaches close to 100% accuracy. Your doctor may also take a small tissue sample during endoscopy for culture testing, which has the added benefit of revealing which antibiotics the bacteria are resistant to.
The Standard Antibiotic Protocol
The current recommended first-line treatment is a 14-day course of what’s called bismuth quadruple therapy. This combines four medications: an acid-reducing drug taken twice daily, tetracycline four times daily, metronidazole three or four times daily, and a bismuth compound (the active ingredient in Pepto-Bismol) four times daily. In a recent randomized controlled trial published in The Lancet, this optimized quadruple therapy achieved a 95% eradication rate.
The older approach, clarithromycin-based triple therapy, used just three drugs and was the standard for years. That regimen now clears the infection only about 81% of the time. The American College of Gastroenterology now specifically recommends against using it unless lab testing has confirmed the bacteria are sensitive to clarithromycin. The reason for this shift is rising antibiotic resistance: clarithromycin resistance exceeds 15% in the majority of countries studied, ranging from 12% to over 90% depending on the region. Metronidazole resistance is even more widespread globally, though the quadruple therapy protocol can often overcome it through higher doses and longer treatment duration.
If the first round fails, alternatives include rifabutin-based therapy and newer regimens using vonoprazan (a more potent acid suppressor) paired with amoxicillin. Your doctor will typically choose a second-line treatment that uses different antibiotics than your first attempt.
What Treatment Feels Like
Taking four medications multiple times a day for two weeks is genuinely demanding. Common side effects include nausea, a metallic taste in your mouth, darkened stools (from the bismuth), and diarrhea. These symptoms are a frequent reason people stop treatment early, which is one of the worst things you can do. Incomplete courses breed antibiotic-resistant bacteria, making the next round harder. Setting phone alarms for each dose and keeping medications in a pill organizer can help you stay on track.
About four weeks after finishing treatment, your doctor will typically retest you with a breath test or stool antigen test to confirm the bacteria are gone. This confirmation step matters because failed eradication is common enough that you shouldn’t assume the infection cleared just because your symptoms improved.
Probiotics as a Treatment Booster
Certain probiotic strains can improve your odds of clearing the infection when taken alongside antibiotics. The best-studied is Limosilactobacillus reuteri (formerly called Lactobacillus reuteri), recognized in the Maastricht V Consensus Report as a beneficial addition to standard therapy. A meta-analysis of 11 randomized controlled trials involving 724 patients found that adding this probiotic significantly increased eradication rates by about 16% compared to antibiotics alone.
Perhaps more importantly, probiotics reduce the gastrointestinal side effects of treatment, including nausea, bloating, and diarrhea. Since side effects are a leading cause of people quitting their antibiotic course early, this indirect benefit may be just as valuable as any direct antibacterial effect. On its own, L. reuteri can reduce the bacterial load but has not been shown to cure an infection without antibiotics.
Dietary Approaches That Show Promise
Broccoli sprouts are the most rigorously studied dietary intervention. They contain high levels of a compound called sulforaphane, which has direct antibacterial effects against H. pylori. In a study published by the American Association for Cancer Research, 48 infected patients ate either 70 grams of broccoli sprouts daily (about 2.5 ounces, roughly a generous handful) or the same amount of alfalfa sprouts as a placebo for eight weeks. The broccoli sprout group showed reduced bacterial colonization and less stomach inflammation. The effect reversed after people stopped eating the sprouts, suggesting this works as ongoing suppression rather than a cure.
Garlic has demonstrated antibacterial activity against H. pylori in laboratory settings thanks to its active compound allicin. However, the concentrations needed in a petri dish don’t translate neatly to what happens in a living stomach, and no clinical trial has shown garlic alone can eradicate the infection.
Manuka honey tells a similar story. Lab studies show that honey with MGO ratings of 400 or higher can inhibit H. pylori growth in culture. But a clinical study in the Saudi Journal of Gastroenterology found that adding manuka honey to standard triple therapy didn’t significantly improve eradication rates. It’s not harmful to include these foods in your diet during treatment, but none of them replace antibiotics for an active infection.
Rebuilding Your Gut After Treatment
A 14-day course of multiple antibiotics doesn’t just kill H. pylori. It disrupts the broader community of beneficial bacteria throughout your digestive tract. Research shows the human gut microbiome is generally resilient and begins recovering even during treatment, with certain resistant bacterial populations temporarily expanding to fill gaps. Full recovery depends heavily on what you eat afterward.
A fiber-rich diet speeds the process significantly. Studies show that a fiber-deficient diet worsens the disruption and delays recovery. Practically, this means prioritizing vegetables, whole grains, legumes, and fermented foods like yogurt, kefir, and kimchi in the weeks following treatment. Exposure to diverse environmental bacteria, including from other household members, also appears to support faster microbial recovery. Most people’s gut communities stabilize within a few weeks to a few months, though the exact timeline varies based on diet and individual factors.
When Stomach Bacteria Aren’t the Problem
Not every case of stomach discomfort involves harmful bacteria. Bloating, heartburn, and nausea have dozens of potential causes, from acid reflux to food intolerances to stress. If you’re experiencing persistent stomach symptoms and haven’t been tested for H. pylori, that’s a reasonable first step since roughly half the world’s population carries this bacterium. But “killing stomach bacteria” without a confirmed infection, whether through leftover antibiotics, herbal supplements, or extreme dietary measures, can do more harm than good by wiping out the beneficial microbes that keep your digestion running smoothly.