Your surgeon will be very careful during surgery to limit the amount of blood you lose. But blood may continue to ooze from tissues that were cut, even after the operation is over. To replace this blood, you may be given a blood transfusion. This is a safe and common procedure, during which you receive blood through an intravenous (IV) line placed in one of your blood vessels.
Several sources of blood are described here.
Blood From the Public (Volunteer Blood Donation)
The most common source of blood given during or after surgery is from volunteers in the general public. This kind of donation is called homologous blood donation. Your blood will be tested to make sure you receive the correct type of donor blood.
Many communities have a blood bank where healthy people can donate blood. This blood is tested to see if it matches yours.
You may have read about the danger of becoming infected with hepatitis, HIV, or other viruses after a blood transfusion. Blood transfusions are not 100% safe. But the current blood supply is thought to be safer now than ever. Donated blood is tested for many different infections. Also, blood centers keep a list of unsafe donors, so the risk of infection from blood transfusions is low.
Donors answer a detailed list of questions about their health before they are allowed to donate. These questions include risk factors for infections that can be passed through their blood, such as sexual habits, drug use, and current and past travel history.