When you throw up blood, where it comes from?

You may find blood in your vomit for various reasons, including:

Ingested blood. If you swallow blood — during a nosebleed, for example — subsequent vomiting may include some of this blood. Prolonged or vigorous vomiting. Vomiting may cause a tear in the small blood vessels of the throat or lower esophagus. This may cause blood to appear in your vomit. Peptic ulcers. Peptic ulcers are open sores that develop on the lining of the stomach, upper small intestine or esophagus. In addition to feeling a burning pain anywhere from your navel to your breastbone, you may vomit blood that appears either red or dark (like coffee grounds). Internal inflammation. Inflamed tissue in the esophagus (esophagitis), stomach (gastritis) or upper part of the small intestine may cause blood to appear in your vomit. Cancer. Various types of cancer may cause you to vomit blood, especially cancers of the stomach and esophagus. Vomiting red blood indicates that the bleeding began shortly before you vomited. If the blood is black or appears dark brown and has the texture of old coffee grounds, the blood has been in your stomach for a longer time.