Anemia is a problem defined as low levels of red blood cells or hemoglobin (the part of the red blood cells that takes oxygen to tissues in the body). Anemia develops when heavy bleeding causes a large iron loss. Anemia can be mild, or severe enough to lead to serious sickness. Blood loss, in the trauma patient, is usually due to fractures (broken bones), or internal organ damage or an operation. These things cause a rapid blood loss called hemorrhage. When a lot of blood is lost in a short time, blood pressure and the amount of oxygen in the body drop quickly. Heart failure and death can follow.