Peptic ulcer disease is the single most common cause of upper gastrointestinal (GI) bleeding, responsible for roughly 44% of all cases. The next largest group, accounting for about 28% of cases, involves non-ulcer damage to the stomach or intestinal lining, such as gastritis and erosions. Esophageal varices, the swollen veins associated with liver disease, cause around 8% of cases. The remaining causes range from tears in the esophagus to tumors and unusual vascular abnormalities.
Peptic Ulcers
An ulcer is an open sore that develops in the lining of the stomach or the first part of the small intestine (the duodenum). When an ulcer erodes deep enough to reach a blood vessel, it bleeds. Two factors are responsible for the vast majority of these ulcers: a bacterial infection called H. pylori and the use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, naproxen, and aspirin.
NSAIDs cause damage in two ways. First, they have a direct topical effect. Most NSAIDs are weak acids, so they pass easily through the protective mucus layer of the stomach and get trapped inside the cells lining the stomach wall, injuring them from the inside. Second, and more importantly, NSAIDs block the production of compounds called prostaglandins that normally keep the stomach protected. Prostaglandins stimulate mucus and bicarbonate secretion, increase blood flow to the stomach lining, and promote cell repair. Without that protection, stomach acid can eat into the tissue.
H. pylori infection works through a different but overlapping path. The bacteria reduce blood flow to the stomach lining, trigger a local inflammatory response, and cause cell death in the mucosal surface. When someone has both H. pylori and takes NSAIDs regularly, each factor makes the lining more vulnerable to the other, compounding the risk significantly.
Gastritis and Mucosal Erosions
Not every case of upper GI bleeding involves a full ulcer. Inflammation of the stomach lining (gastritis) or shallow erosions in the stomach and duodenum account for more than a quarter of all cases. These lesions don’t penetrate as deeply as ulcers, so the bleeding tends to be less severe, but it can still be enough to cause symptoms. Common triggers include heavy alcohol use, stress from critical illness or major surgery, bile reflux, and the same NSAID use that causes ulcers. The distinction between erosions and ulcers is largely one of depth: erosions stay within the superficial lining, while ulcers dig into the deeper tissue layers where larger blood vessels sit.
Esophageal Varices
Varices are swollen, fragile veins in the lower esophagus that develop when blood can’t flow normally through the liver. The most common reason for this is cirrhosis, where scarring stiffens the liver and increases the pressure in the vein that feeds it (the portal vein). When that pressure builds, blood reroutes through smaller veins that weren’t designed to handle the load, including veins in the esophageal wall. Over time, those veins balloon outward, becoming thin-walled and prone to rupture.
When varices rupture, the bleeding is often massive and life-threatening. Variceal rupture is the most common fatal complication of cirrhosis, and the severity of the liver disease directly correlates with the likelihood that varices will form and eventually bleed. People with advanced cirrhosis, significant fluid retention, or signs of liver failure are at the highest risk.
Mallory-Weiss Tears
A Mallory-Weiss tear is a split in the lining of the esophagus or upper stomach, usually right at the junction where the two meet. The tear happens when intense pressure builds up during forceful or prolonged vomiting, severe coughing, or retching. Heavy drinking followed by repeated vomiting is a classic trigger. Epileptic seizures and violent hiccups can also cause these tears. Most Mallory-Weiss tears stop bleeding on their own, but some are deep enough to require treatment.
Blood Thinners and Antiplatelet Drugs
Medications that prevent clotting don’t typically cause GI bleeding by themselves. Instead, they amplify bleeding from damage that already exists. If you have a small erosion or mucosal break that would normally heal without symptoms, an anticoagulant or antiplatelet drug can turn it into a clinically significant bleed. Research from the American Heart Association found that combination blood-thinning therapies increase the risk of upper GI bleeding by 40% to 60% compared to people not taking these drugs. Aspirin is particularly notable because it both thins the blood and directly injures the stomach lining, acting as both the cause of mucosal damage and the reason the damage bleeds more than it should.
Cancer of the Stomach or Esophagus
Tumors in the esophagus or stomach can bleed as they grow into surrounding tissue. In people already diagnosed with esophageal cancer, tumor-related bleeding is actually the most common cause of upper GI bleeding episodes, responsible for over half of cases in that group. For the broader population, cancer is a less frequent cause, but it’s an important one because upper GI bleeding sometimes turns out to be the first sign of an undiagnosed tumor. This is one reason doctors generally recommend an endoscopy for people over 50 who develop new or unexplained GI bleeding.
Dieulafoy’s Lesion
This is a rare but notable cause. A Dieulafoy’s lesion is an abnormally large artery, typically 1 to 3 millimeters wide, that runs just below the surface of the stomach wall. Unlike an aneurysm, the vessel itself is structurally normal. It simply never tapered down to the small size expected for that location. The artery sits beneath a tiny defect in the overlying lining, sometimes only 2 to 5 millimeters across, and can suddenly erode through and bleed heavily. These lesions are notoriously hard to find. Initial endoscopy catches them about 70% of the time, and 6% of patients need three or more procedures before the source is identified. In more than half of missed cases, the lesion was simply too subtle to see; in the rest, blood in the stomach obscured the view.
How the Symptoms Differ by Cause
Upper GI bleeding shows up in a few recognizable ways, and the type of symptom gives clues about where and how much you’re bleeding. Vomiting blood (hematemesis) confirms the source is above the first portion of the small intestine. Vomiting bright red blood generally signals a larger, more active bleed, while vomiting material that looks like dark coffee grounds suggests the blood has been partially digested by stomach acid, pointing to slower bleeding. In one study, every patient who vomited blood had already lost more than a quarter of their red blood cell volume.
Black, tarry, foul-smelling stools (melena) are the most common presenting symptom of significant upper GI bleeding. The dark color comes from blood being broken down as it passes through the digestive tract. Melena strongly suggests an upper GI source, though very slow bleeding from the first part of the large intestine can occasionally produce it as well. Bright red blood in the stool is less typical for upper GI bleeding and usually points to a source in the colon, but it can occur with a very fast upper GI bleed where blood moves through the intestines quickly.
The combination of vomiting red blood along with melena, or vomiting red blood alone, typically indicates a major hemorrhage that needs urgent evaluation.