Vomiting blood (hematemesis) refers to significant amounts of blood in your vomit. Small streaks or flecks of blood in material you spit up or cough up isn't usually considered vomiting blood. Blood in vomit may be bright red, or it may appear black or dark brown like coffee grounds.
While vomiting blood may be caused by swallowed blood, as from a nosebleed or forceful coughing, truly vomiting blood usually represents something more serious and requires immediate medical attention. Bleeding in your upper gastrointestinal tract (mouth, esophagus, stomach and upper small intestine) from peptic ulcers or torn blood vessels is a common cause of vomiting blood. Call 911 if vomiting blood causes dizziness after standing, rapid, shallow breathing or other signs of shock.