Here is some information I found on the AABB website (http://www.aabb.org) Preoperative Donation The most common autologous donation is the preoperative donation of blood for possible transfusion back to the donor during elective surgery. For example, a person might give one unit of blood each week for up to six weeks before surgery, because blood can be stored in its liquid form for up to 42 days. Patients can make autologous donations up until 72 hours prior to their surgery. This is to allow the body enough time to replenish its blood supply before the surgical procedure. A significant amount of iron is removed with each autologous donation. When appropriate, iron supplements are prescribed for patients making autologous donations in order to help increase red blood cell count. Autologous donation is most often employed in surgery on bones, blood vessels, the urinary tract, and the heart, when the likelihood of transfusion is high. According to the National Blood Data Resource Center, autologous blood accounted for 4.7 percent of all donated blood in 1999. Potential autologous blood donors are medically stable patients who are free of infection. There is no age limitation for autologous donation. Many children and elderly patients have successfully completed autologous donations; however, some patients may not be good candidates. The physician and patient should make the decision regarding autologous donation and transfusion jointly. The process of donating autologous blood stimulates the bone marrow to produce new blood cells. Given adequate time for recovery, the collected cells may be wholly or partially replaced prior to surgery. If blood loss during surgery is less than anticipated, transfusion of autologous blood may not be medically necessary. Although the risk of a complication from autologous blood is low, some residual risk persists, making automatic transfusion of autologous units unwise. Forty-four percent of autologous donations are unused by the autologous donor. These units generally are discarded because current standards do not allow transfusion of these units to another patient for safety reasons. In emergency situations, however, these units may be used for another patient provided there is medical approval for the crossover and the unit has been fully screened. Due to the special handling and separate storage requirements, autologous donations cost more to process. Hope it helps