Bleeding refers to the loss of blood. Bleeding can happen inside the body (internally) or outside the body (externally). It may occur:

• Inside the body when blood leaks from blood vessels or organs
• Outside the body when blood flows through a natural opening (such as the vagina, mouth, or rectum)
• Outside the body when blood moves through a break in the skin

Internal bleeding can rapidly become life threatening, and immediate medical care is needed. People who take blood-thinning medication or who have a bleeding disorder such as hemophilia may bleed excessively and quickly because their blood does not clot properly. Bleeding in such people requires immediate medical attention. Abdominal and chest wounds can be very serious because of the possibility of severe internal bleeding. They may not look very serious, but can result in shock. Seek immediate medical care immediately for any abdominal or chest wound.

Bleeding can be caused by injuries or can occur spontaneously. Spontaneous bleeding is most commonly caused by problems with the joints or the gastrointestinal or urogenital tracts.