How Much Blood Can a Person Lose Before Dying?

A person who loses approximately 40 percent or more of his blood volume needs immediate emergency care; otherwise, the strain on the circulatory system becomes fatal, explains Medical Daily. Known as class 4 hemorrhaging, this condition prevents the heart from maintaining pressure for circulation, and the vital organs soon begin to fail. A person with this much blood loss goes into hypovolemic shock, and even if under care, the prognosis depends on various underlying factors.

The body protects itself in the case of such extensive blood loss by recirculating blood from the limbs to the torso and brain, explains Medical Daily. A person can also apply pressure externally to a hemorrhaging wound to slow the bleeding. Class 3 hemorrhaging, in which a person loses between 30 and 40 percent of blood volume, also poses serious dangers and risks, although it is usually not fatal with timely medical care. The condition makes the blood pressure drop significantly and commonly requires a blood transfusion to stabilize the patient.

Class 2 hemorrhaging, which involves a 15- to 30-percent loss of blood volume, can also have significant consequences, such as an increased heartbeat and a pale cast to the skin, but the patient is under no serious health threat if it is properly attended to, reports Medical Daily. Individuals with class 1 hemorrhaging may show no symptoms at all.