It's becoming increasingly common to donate your own blood to be used during surgery, when your operation is scheduled far enough in advance. This method is known as autologous (aw-TOL-oh-guss) donation. The main benefit is that your body won't reject or react adversely to your own blood, a problem that can occur with a foreign donor. In addition, you escape the risk, however slim, of contracting any infectious diseases through a blood transfusion. Sometimes, self-donation may be necessary, if your blood type is rare, and doctors can't obtain a sufficient amount from a blood bank. Autologous donation works best for individuals of normal weight, with plenty of oxygenated red cells in their blood. Certain health conditions will prevent you from self-donating, including angina, severe heart disease, bacterial infections, cancer, or other major disorders like respiratory or kidney disease. Assuming you meet the medical criteria, you'll need to donate blood over a period of three to five weeks. After each visit, the collected blood will be labeled and refrigerated, until your surgery. Your bone marrow will make new blood cells, to restore what was lost. To find out more about donating blood before surgery, speak to your doctor.