Hemorrhage is an acute loss of blood from any site in the body. Trauma to major arteries, veins, or the heart may lead to massive hemorrhage.

Gastrointestinal tract hemorrhage is usually accompanied by loss of altered blood in vomit or feces and may lead to shock; ulcers and bowel cancer are important causes. Antepartum hemorrhage is blood loss from the uterus (womb) in late pregnancy and may rapidly threaten the life of both mother and fetus; postpartum hemorrhage is excessive blood loss after birth due to inadequate womb contraction or retained placenta.

Stroke due to brain hemorrhage may damage vital structures and cause coma, while subarachnoid bleeding around the brain from aneurysm or malformation causes severe headache. Fractures may cause sizeable hemorrhage into soft tissues. Blood loss may be replaced by transfusion, and any blood clots may need to be removed.