Bleeding ulcers are most commonly caused by a bacterial infection called H. pylori or by regular use of common pain relievers like ibuprofen and naproxen. These two factors account for the vast majority of peptic ulcers that eventually bleed, though blood-thinning medications, alcohol use, and rare conditions can also play a role. In the United States, roughly 54,000 people are hospitalized each year due to peptic ulcer bleeding.
H. pylori Infection
H. pylori is a spiral-shaped bacterium that burrows into the mucus lining of your stomach and small intestine. Once established, it damages the protective barrier that keeps digestive acid away from the tissue underneath. Without that barrier, stomach acid eats into the exposed tissue and creates an open sore. About 10% to 15% of people infected with H. pylori eventually develop an ulcer, and any ulcer that goes deep enough can erode into a blood vessel and start bleeding.
Many people carry H. pylori for years without symptoms. The infection spreads through contaminated food, water, or close contact, and it’s more common in areas with crowded living conditions or limited sanitation. When an ulcer does form, it often develops in the first part of the small intestine (the duodenum) or in the stomach itself. Treatment involves a combination of antibiotics to kill the bacteria and acid-reducing medication to let the ulcer heal.
Pain Relievers and Anti-Inflammatory Drugs
Over-the-counter pain relievers known as NSAIDs are the second leading cause of bleeding ulcers. These drugs work by blocking an enzyme your body uses to produce compounds called prostaglandins. That’s how they reduce pain and inflammation, but prostaglandins also maintain the protective mucus layer in your stomach. When NSAID use suppresses that layer, stomach acid can reach the tissue underneath and cause erosion.
Not all NSAIDs carry equal risk. Naproxen has the highest relative risk for upper gastrointestinal bleeding or perforation (about 5.6 times the baseline risk), followed by diclofenac (4.0 times) and ibuprofen (2.7 times). Newer drugs designed to target inflammation more selectively carry a lower risk (about 1.9 times baseline), though they aren’t risk-free. The danger increases with higher doses, longer use, and older age. Taking an NSAID on an empty stomach or combining it with alcohol makes matters worse.
Blood Thinners and Antiplatelet Drugs
If you already have an ulcer, even a small one, blood-thinning medications can turn it into a serious bleed. Drugs like aspirin and clopidogrel prevent blood clots by reducing platelet activity, which is exactly why they’re prescribed after heart attacks or stent placement. But that same effect means your body is slower to seal off a damaged blood vessel in the stomach lining. The relative risk of upper gastrointestinal bleeding increases by up to 10% in patients on these therapies, with annual bleeding rates between 1.5% and 4.5%.
This creates a difficult tradeoff. Stopping a blood thinner reduces bleeding risk but can be dangerous for the heart, especially within the first year after a coronary stent. When a bleeding ulcer does occur in someone on these medications, doctors typically pause the drug briefly, but aspirin prescribed for established heart disease is usually restarted within one to seven days. Clopidogrel is particularly tricky to stop, since discontinuing it raises the risk of stent clotting and heart attack.
Alcohol Consumption
Regular alcohol use is an independent risk factor for ulcer bleeding. A large prospective study of men found that even moderate drinking (one to two drinks per day) raised the risk of major upper gastrointestinal bleeding by about 76% compared to nondrinkers. Beer and liquor at five or more drinks per day were specifically linked to bleeding from peptic ulcers, with beer carrying roughly double the risk.
Alcohol irritates the stomach lining directly and increases acid production. Over time, it weakens the mucus barrier much the way NSAIDs do. Combined with other risk factors like H. pylori infection or regular NSAID use, heavy drinking substantially compounds the chance of a bleed.
Stress Ulcers in Critical Illness
The kind of stress that causes bleeding ulcers isn’t everyday work pressure or anxiety. Stress ulcers develop in people who are critically ill, typically in an intensive care unit after major surgery, severe burns, head injuries, or organ failure. The mechanism is straightforward: during extreme physiological stress, blood flow to the stomach lining drops sharply. This starves the mucus-producing cells of oxygen and nutrients, and the protective barrier breaks down.
Contrary to what you might expect, acid production in these patients is usually normal or even decreased. The problem isn’t too much acid. It’s that the defense system has collapsed, so even normal amounts of acid can damage the exposed tissue. Older adults are particularly vulnerable because age-related narrowing of blood vessels further reduces blood supply to the stomach lining, making it harder to maintain that mucus barrier under stress.
Zollinger-Ellison Syndrome
In rare cases, bleeding ulcers are caused by a tumor called a gastrinoma that produces massive amounts of a hormone (gastrin) that tells the stomach to make acid. This condition, known as Zollinger-Ellison syndrome, floods the stomach and upper intestine with far more acid than the lining can withstand. The result is multiple ulcers, often in unusual locations further down the intestine than typical ulcers, with a high rate of bleeding, perforation, and scarring.
Zollinger-Ellison syndrome is diagnosed by measuring gastrin levels in the blood after fasting. A level above 1,000 pg/mL with a highly acidic stomach (pH of 2 or below) is considered classic. Because standard acid-reducing medications can mask the lab results, they usually need to be stopped for at least a week before testing. This condition should be suspected in anyone who develops recurrent or unusually severe ulcers that don’t respond to normal treatment.
Dieulafoy Lesions
A Dieulafoy lesion is a rare but dangerous cause of sudden, massive gastrointestinal bleeding. It involves a normal blood vessel that happens to be abnormally wide (1 to 3 millimeters, much larger than surrounding vessels) and sits just beneath the stomach lining. Over time, the pulsing of this oversized artery can wear through the thin tissue above it, exposing the vessel to stomach acid and digestive contents. The result is erosion and heavy bleeding that can appear without warning.
Unlike typical ulcers, Dieulafoy lesions are tiny and easy to miss on examination when they’re not actively bleeding. They’re more common in older adults, possibly because the stomach lining thins with age, making it easier for a large underlying vessel to break through.
How to Recognize a Bleeding Ulcer
A bleeding ulcer announces itself through changes you can see. The most common sign is black, tarry stools that have a distinctive stickiness. This happens when blood from the stomach or upper intestine is digested on its way through the gut, turning it dark. It takes at least 50 milliliters of blood (a few tablespoons) to produce this color change.
Vomiting blood is another clear signal. The vomit may be bright red if bleeding is heavy and active, or it may look like dark coffee grounds if the blood has been sitting in the stomach and partially digested. In cases of very rapid bleeding, fresh red blood can even appear in your stool rather than turning it black, because the blood moves through the intestine too fast to be broken down. Any of these signs, especially combined with lightheadedness, rapid heartbeat, or sudden weakness, points to significant blood loss.