Blood transfusions take place in either a doctor's office or a hospital. Sometimes they're done at a person's home, but this is less common. Blood transfusions also are done during surgery and in emergency rooms.
A needle is used to insert an intravenous (IV) line into one of your blood vessels. Through this line, you receive healthy blood. The procedure usually takes 1 to 4 hours. The time depends on how much blood you need and what part of the blood you receive.
During the blood transfusion, a nurse carefully watches you, especially for the first 15 minutes. This is when allergic reactions are most likely to occur. The nurse continues to watch you during the rest of the procedure as well.