Bleeding Through Mouth
This can range from a life-threatening bleed to a trickle. Sudden, heavy bleeding causes you to cough blood (this is called haematemesis) and make you feel very weak. It can be an indication of a perforated stomach ulcer.
More rapid bleeding will cause you to vomit. In most cases, vomit appears coffee-colored as the blood is partly broken down by the stomach acid. A more gradual blood trickle will pass through your gut (bowel) and make your stools (feces) look very dark or even black (a gut condition known as melena).