Blood in the stomach, also known as gastrointestinal (GI) bleeding, can occur due to a number of possible reasons. It can be a symptom of a serious condition and may require immediate medical care. Possible causes Hemorrhoids Peptic ulcers Inflammation or tears in the esophagus Diverticulosis and diverticulitis Ulcerative colitis and Crohn's disease Colonic polyps Cancer in the stomach, esophagus, or colon Symptoms Visible blood in vomit or stool, Changes in stool color, Vomiting red or black bl