What is a blood transfusion?

Blood transfusion is a medical treatment that replaces blood lost through injury, surgery, or disease. The blood goes through a tube from a bag to an intravenous (IV) catheter and into your vein.

When is a blood transfusion needed?

You may need a blood transfusion if you lose too much blood, such as through:

• Injury or major surgery.
• An illness that causes bleeding, such as a bleeding ulcer.
• An illness that destroys blood cells, such as hemolytic anemia or thrombocytopenia.

If you have an illness in which your bone marrow doesn't make enough blood, such as aplastic anemia, you may need transfusions. Some diseases, such as hemophilia, prevent your body from making a needed blood component. Components are the different parts of blood, such as red blood cells, plasma, and platelets. You may need transfusions or injections of the missing blood component to help treat these diseases.

Is a blood transfusion safe?

Blood used for transfusions in the United States is very safe and generally free from disease. Donated blood is carefully tested. It is very rare to get a disease through a blood transfusion.

Getting the wrong blood type by accident is the main risk in a blood transfusion, but it is rare. Getting the wrong blood type happens about once in every 14,000 transfusions.¹ Transfusion with the wrong blood type can cause a severe reaction that may be life-threatening.

Some people bank their own blood a few weeks before they have surgery. If they need a transfusion during surgery, they can receive their own banked blood. This reduces the risk of disease and transfusion reaction from donated blood.

If you have many blood transfusions, you are more likely to have problems from immune system reactions. A reaction happens when your body rejects the new blood and tries to attack parts of it. But tests can help avoid this. Before you get a blood transfusion, your blood is tested to find out your blood type. And the blood you will get in the transfusion is tested to make sure it matches your blood.

You may have a mild allergic reaction even if you get the correct blood type. Signs of a reaction include:

• A fever.
• Hives.
• Shortness of breath.
• Pain.
• A fast heart rate.
• Chills.
• Low blood pressure.

A mild reaction can be scary, but it rarely is dangerous if it’s treated quickly.

What are blood types, and why are they important?

The most important blood type classification systems are the ABO system and the Rh system. A, B, AB, and O are the blood types in the ABO system. Each type of blood in the ABO system also has a positive or negative Rh factor. For example, if you have "A+ blood," it means your blood is type A in the ABO system and your Rh factor is positive.