What is a blood transfusion?

A blood transfusion involves receiving donated blood or blood parts into your body through one of your blood vessels. A needle is put into a vein, often in the arm. The needle is attached to a thin, flexible tube (catheter). This is called an IV (intravenous) line. Blood is sent into your vein through this IV line.

Your blood has several parts. Plasma is the liquid part of your blood. It’s made of water, proteins, clotting factors, hormones, and other substances.

Floating in the plasma are many red blood cells (RBCs). These cells contain hemoglobin. Hemoglobin lets RBCs carry oxygen from your lungs to the rest of your body. Your whole body needs oxygen, so it’s important to have enough RBCs.

Your blood also contains white blood cells. These larger cells help the body fight infection.

And your blood contains cells even smaller than red blood cells called platelets. These help the blood clot. Proteins called clotting factors also help your blood clot. Without these, your body can’t stop bleeding from even a tiny wound.

Whole blood refers to blood with all these parts. Most of the time, a blood transfusion is done with only part of the blood. You might be given one or more of these blood parts based on your needs.

When you have a blood transfusion, it’s important to be given blood that is compatible with (matches) your blood. Blood comes in four main types: A, B, AB, and O. These types refer to molecules called antigens on the surfaces of blood cells. Antigens are substances that can cause a person’s immune system to react. Type A blood has the A antigen. Type B blood has the B antigen. Type AB blood has both A and B antigens. Type O blood has neither A nor B antigens.

Rh factor is another type of antigen. Blood is either Rh positive or Rh negative. Each person’s blood is 1 of 8 specific types: A+, A−, B+, B−, AB+, AB−, O+, and O−.

If a person gets the wrong type of blood, their immune system will react to it. This is a serious condition that can cause severe symptoms, such as fever, rash, muscle aches, and trouble breathing. It can sometimes be fatal.

People with O− blood don't have A, B, or Rh molecules on their blood cells. These people can donate blood to anyone. They are known as universal donors.

People who are AB+ have all 3 molecules (A, B, and Rh) on their blood cells and can safely receive blood from anyone.

You can only get blood products that are compatible with your blood type. A sample of your blood is tested for compatibility with donated blood. This is done before blood products are prepared for a transfusion.

Why might you need a blood transfusion?

You might need a blood transfusion if you’ve had a problem such as:

• A serious injury that’s caused major blood loss.

• Surgery that’s caused a lot of blood loss.

• Blood loss after childbirth.

• A liver problem that makes your body unable to create certain blood parts.

• A bleeding disorder, such as hemophilia.

• An illness that causes reduced or poor-quality RBCs (anemia).

• Kidney failure, which causes problems with blood cell production.

• Treatment for cancer (chemotherapy) that slows down your body’s production of blood cells.

Different medical problems may need different types of blood transfusions. For example, after surgery you may need just RBCs. You might need plasma if you have a bad infection. A person being treated for cancer may need platelets. Your health care provider can tell you why you need a blood transfusion and which type is best for you.

What are the risks of blood transfusions?

All procedures have some risks. The risks of blood transfusions include:

• An allergic reaction. This can be mild or severe. Mild symptoms can include itching or rash. Severe symptoms can include trouble breathing, chest pain, or nausea. These symptoms may start soon after your blood transfusion or within the next 24 hours.

• Fever. This can happen within a day of the blood transfusion. It’s usually temporary.

• Destruction of red blood cells by the body (hemolytic reaction). A hemolytic reaction happens when your body attacks the donated RBCs. This happens if you get a blood type that your blood isn’t compatible with. Donated blood goes through a very careful matching process, so this reaction is very rare. If it does happen, it can cause chills, fever, kidney damage, and other serious symptoms. Symptoms can happen during the blood transfusion or in the next several hours. A delayed hemolytic reaction can also happen. This can happen even if you got the right blood type. This may take days or weeks to happen. It may not cause any symptoms, but it can cause your RBC count to be lower.

• Too much blood in the body (transfusion overload). Transfusion overload may happen if a person gets more blood than needed. It can cause shortness of breath and other symptoms. The symptoms usually happen within a few hours to a day. It’s more common in people with heart problems. Taking diuretic medicine after a blood transfusion may prevent this problem.

• Too much iron in the body (iron overload). This can happen in people who need to have many blood transfusions over time for an ongoing medical condition.

• Viruses being transmitted. The viruses can include HIV or hepatitis. Blood goes through a very careful screening before blood transfusions. The risk of a virus being passed on is very low.

• Graft-versus-host disease. This is a condition where the new, donated blood cells attack cells in the body. It’s a serious but rare condition. Symptoms such as fever and rash may start within a month of the blood transfusion.

Your own risks may vary according to your general health, the type of blood transfusion, and whether you’ve had a blood transfusion before. Talk to your health care provider about which risks may apply to you.

How do you get ready for a blood transfusion?

You likely won’t need to do much to get ready for your blood transfusion. Your health care provider will let you know if you need to prepare in any way.

Make sure to tell them if you have ever had a bad reaction to a blood transfusion. You may be given a medicine to help prevent an allergic reaction.

Most hospitals need a consent form before a blood transfusion. This needs to be signed by you or by a chosen family member.

Your blood will be tested before the blood transfusion to find out what type it is. This is to make sure that you get donor blood compatible with yours. Your finger may be pricked to get a few drops of blood. Or you may have blood taken from a vein in your arm.

What happens during a blood transfusion?

During the procedure, you will be given blood from one or more people who donated it. In some cases, you may be given blood that was taken from you before. Or you may be given blood from a family member or friend.

A health care provider will clean the area where the IV will go. They will insert an IV into one of your veins, most likely in your arm. The whole blood or blood parts will be sent through this line. The whole process may take 1 to 4 hours.

A provider will keep track of your vital signs and watch you for any signs of negative reactions. These are most likely in the first 15 minutes. Tell the provider right away if you start having symptoms.

You should be able to eat, drink, and go to the bathroom with help during the procedure. Your provider will let you know about what else to expect.

What happens after a blood transfusion?

After your blood transfusion, your vital signs will be checked. These include your heart rate, breathing, temperature, and your blood pressure. The health care provider will remove your IV.

You may be able to go home soon after your blood transfusion. You should be able to go back to your normal activities and eat a normal diet. Your provider may give you additional instructions.

The area on your arm where you had the IV may be sore for a few hours. Tell your provider right away if you have fever, trouble breathing, swelling at the IV site, or other symptoms.

You may need to have follow-up blood tests. This is to see how your body is responding to the blood transfusion.

Next steps

Before you agree to the test or procedure, make sure you know:

• The name of the test or procedure.

• The reason you are having the test or procedure.

• What results to expect and what they mean.

• The risks and benefits of the test or procedure.

• What the possible side effects or complications are.

• When and where you are to have the test or procedure.

• Who will do the test or procedure and what that person’s qualifications are.

• What would happen if you did not have the test or procedure.

• Any alternative tests or procedures to think about.

• When and how will you get the results.

• Who to contact after the test or procedure if you have questions or problems.

• How much you will have to pay for the test or procedure.