What Is a Blood Transfusion?

A blood transfusion is a safe, common procedure in which blood is given to you through an intravenous (IV) line in one of your blood vessels.
Blood transfusions are done to replace blood lost during surgery or due to a serious injury. A transfusion also may be done if your body can't make blood properly because of an illness.
During a blood transfusion, a small needle is used to insert an IV line into one of your blood vessels. Through this line, you receive healthy blood. The procedure usually takes 1 to 4 hours, depending on how much blood you need.
Blood transfusions are very common. Each year, almost 5 million Americans need a blood transfusion. Most blood transfusions go well. Mild complications can occur. Very rarely, serious problems develop.
Important Information About Blood
The heart pumps blood through a network of arteries and veins throughout the body. Blood has many vital jobs. It carries oxygen and other nutrients to your body's organs and tissues. Having a healthy supply of blood is important to your overall health.
Blood is made up of various parts, including red blood cells, white blood cells, platelets (PLATE-lets), and plasma. Blood is transfused either as whole blood (with all its parts) or, more often, as individual parts.
Blood Types
Every person has one of the following blood types: A, B, AB, or O. Also, every person's blood is either Rh-positive or Rh-negative. So, if you have type A blood, it's either A positive or A negative.
The blood used in a transfusion must work with your blood type. If it doesn't, antibodies (proteins) in your blood attack the new blood and make you sick.
Type O blood is safe for almost everyone. About 40 percent of the population has type O blood. People who have this blood type are called universal donors. Type O blood is used for emergencies when there's no time to test a person's blood type.
People who have type AB blood are called universal recipients. This means they can get any type of blood.
If you have Rh-positive blood, you can get Rh-positive or Rh-negative blood. But if you have Rh-negative blood, you should only get Rh-negative blood. Rh-negative blood is used for emergencies when there's no time to test a person's Rh type.
Blood Banks
Blood banks collect, test, and store blood. They carefully screen all donated blood for possible infectious agents, such as viruses, that could make you sick. (For more information, see "What Are the Risks of a Blood Transfusion?")
Blood bank staff also screen each blood donation to find out whether it's type A, B, AB, or O and whether it's Rh-positive or Rh-negative. Getting a blood type that doesn't work with your own blood type will make you very sick. That's why blood banks are very careful when they test the blood.
To prepare blood for a transfusion, some blood banks remove white blood cells. This process is called white cell or leukocyte (LU-ko-site) reduction. Although rare, some people are allergic to white blood cells in donated blood. Removing these cells makes allergic reactions less likely.
Not all transfusions use blood donated from a stranger. If you're going to have surgery, you may need a blood transfusion because of blood loss during the operation. If it's surgery that you're able to schedule months in advance, your doctor may ask whether you would like to use your own blood, rather than donated blood.
If you choose to use your own blood, you will need to have blood drawn one or more times prior to the surgery. A blood bank will store your blood for your use.
Alternatives to Blood Transfusions
Researchers are trying to find ways to make blood. There's currently no man-made alternative to human blood. However, researchers have developed medicines that may help do the job of some blood parts.
For example, some people who have kidney problems can now take a medicine called erythropoietin that helps their bodies make more red blood cells. This means they may need fewer blood transfusions.
Surgeons try to reduce the amount of blood lost during surgery so that fewer patients need blood transfusions. Sometimes they can collect and reuse the blood for the patient.