Bright red streaks of blood in vomit can be caused by a nosebleed or irritation in your throat when you vomit. This is not serious if there is only a small streak of blood that you are sure came from your mouth or nose.

However, if there is more than a streak of blood, bleeding continues, or you are not sure the blood came from your mouth or nose, you should see your doctor.

A moderate to large amount of blood in your vomit indicates bleeding in the upper digestive tract (gastrointestinal, or GI, tract), usually from the esophagus or stomach. Digestive tract bleeding can be caused by inflammation, an open sore (ulcer) in the lining of your stomach or intestine, throat irritation from vomiting, or bleeding from enlarged esophageal veins (esophageal varices). If bleeding is severe, the vomit will be mostly blood or partly digested blood, which looks like coffee grounds.

Heartburn can cause bleeding inside the esophagus if persistent heartburn has caused ulcers to form in the esophagus.

Heartburn may occur at the same time as other illnesses (such as peptic ulcer disease or gastritis) that cause ulcers or inflammation in the stomach or the part of the small intestine that connects to the stomach (duodenum). These illnesses may cause abdominal pain and, occasionally, large amounts of blood in the vomit.