Patient education: Blood transfusion (The Basics)

What is a blood transfusion? — This is when a person gets donated blood. You might need donated blood if you:

●Lost a lot of blood, for example, in an accident or during surgery

●Have a medical condition that affects your blood

Blood is made up of different parts:

●Red blood cells carry oxygen to the body.

●White blood cells help fight infections.

●Platelets help the blood to clot.

●Plasma is the liquid part of the blood. It contains many types of proteins. Some of these proteins help the blood to clot.

When someone donates blood, the parts are separated into "components." This way, the person receiving the transfusion only gets what they need. Most of the plasma is removed from the red blood cells to create a unit of "packed red blood cells," or "pRBCs." Usually, when people say "blood transfusion," they mean transfusion of pRBCs.

Getting only the component you need avoids exposing you to things you do not need. It also means that the other components can be given to other people who might need them.

Less commonly, a person might get a transfusion with "whole blood." This is blood that has not been separated into different components.

Where does the blood come from? — Most of the time, blood for a transfusion comes from a blood collection center (sometimes called a "blood bank"). This center might be part of a hospital or it might be separate. When people donate blood, it goes to 1 of these centers. Then, it is tested, made ready to use, and stored until it is needed.

In some cases, a person can donate their own blood. The blood can be stored for their own use if they are planning to have surgery soon. That way, if they need a blood transfusion, they can get their own blood.

How do I know that the blood is safe? — Before your blood transfusion, you will have a blood test to check your "ABO blood type" (A, B, AB, or O). This also involves checking for a specific protein that some people have on their red blood cells, called the "RhD antigen." If your blood has this protein, it is called "Rh-positive," and if it does not, it is called "Rh-negative."

The donated blood is tested for ABO type and RhD, too. This is to make sure that you get a unit of packed red blood cells that is "compatible" with your blood type. If the blood is not compatible, your immune system could attack the new red blood cells and make you sick.

People who donate blood must answer questions to learn if they are at a higher risk for some infections. The blood bank also tests the donated blood for the bacteria that causes syphilis and for certain viruses. Some of these include HIV, hepatitis B virus, hepatitis C virus, and West Nile virus. They do not test the blood for the virus that causes COVID-19.

What happens during a blood transfusion? — You get the donated blood component through an "IV" (a thin tube that goes into a vein) (figure 1). A blood transfusion can take up to 4 hours, depending on how much blood you need and how quickly you need it. The staff will closely watch your heart rate, blood pressure, and temperature while you get the blood.

What are the risks of blood transfusion? — Risks include:

●Allergic reactions, fever, or hives

●Shortness of breath if your body has trouble handling extra fluids

●A reaction in the lungs that affects breathing

●The immune system attacking donated red blood cells

●An infection for which the blood is not screened, or a bacterial infection

What else should I know? — Tell your doctor right away if you have any symptoms during your transfusion that might mean there is a problem. Most of these reactions happen during the transfusion or within a few hours afterward.

Tell your doctor or nurse right away if you have:

●Signs of a very bad reaction – These include wheezing, trouble breathing, chest or back pain or tightness, fever, itching, bad cough, seizures, or swelling of face, lips, tongue, or throat. If you have any of these symptoms after your transfusion, call for an ambulance right away (in the US and Canada, call 9-1-1).

●Signs of infection – These include a fever of 100.4°F (38°C) or higher or chills. Very rarely, this could happen days to weeks after the transfusion.

●Headache or dizziness

●Itching or a rash

●Urine that looks red or dark in color

More on this topic

Patient education: Blood donation (giving blood) (The Basics)
Patient education: Blood type test (The Basics)
Patient education: Red blood cell antibody screening (The Basics)

Patient education: Blood donation and transfusion (Beyond the Basics)