Peptic Ulcer Disease: This is often the most common cause of bloody vomit, especially in adults. The bleeding can be due to a gastric or duodenal ulcer, and the presentation can range from mild to life-threatening.

Gastroesophageal Varices: These are dilated veins in the esophagus that can bleed easily, often due to liver cirrhosis. The bleeding can be severe and is a medical emergency.
Mallory-Weiss Syndrome: This condition involves tears in the mucous membrane or lining of the lower end of the esophagus, where it connects to the stomach. These tears can bleed, and the condition is often associated with intense or prolonged vomiting, retching, or coughing.
Gastritis: Inflammation of the stomach lining can cause bleeding, leading to bloody vomit. This can be due to various causes, including alcohol use, medications like NSAIDs, or infections.

Esophageal Cancer: Although less common, esophageal cancer can cause bloody vomit and is critical to diagnose early for treatment.
Aortic Enteric Fistula: A rare but potentially fatal condition where there's a connection between the aorta and the intestine, leading to severe bleeding.
Boerhaave's Syndrome: A rupture of the esophagus, which can lead to severe bleeding and is a medical emergency.

Dieulafoy's Lesion: A rare cause of gastrointestinal bleeding characterized by a small mucosal defect with an exposed, often large, caliber artery at its base.
Hemobilia: Bleeding into the biliary tree, which can lead to bloody vomit, though this is more commonly associated with bloody stools.
Osler-Weber-Rendu Syndrome (Hereditary Hemorrhagic Telangiectasia): A genetic disorder that leads to the formation of abnormal blood vessels, which can cause bleeding in various parts of the body, including the gastrointestinal tract.