I just got my first batch of papers from the doctor about my upcoming hip replacement surgery. It says I'm supposed to donate two units of blood for myself before the operation. Will I really bleed that much?

Patients having a total hip (or total knee) replacement can lose up to one-third of their total red blood cell volume. Blood transfusion is often needed after joint replacement surgery.

In many centers it's common to ask patients to predonate blood for their own operation. This helps avoid passing any viruses through the blood. It also eliminates any bad reactions to another person's blood.

Before using any blood transfusions, the patient's own blood lost during the operation is used. The blood is collected and measured. If enough is lost, then the drained blood is filtered and reinfused into the patient. Extra blood transfusion is only needed when there is more blood lost than can be reinfused.