When you get a blood transfusion, you receive blood via an intravenous (IV) line. Blood transfusions are sometimes necessary after an injury or surgery causes a high amount of blood loss. Some people need regular transfusions due to medical conditions such as hemophilia or cancer. This is called transfusion therapy.

According to the National Heart, Lung, and Blood Institute, about 5 million Americans need a blood transfusion each year.

Prior to any blood transfusion, laboratory tests must ensure that donor blood is compatible with yours. Transfusion therapy can take place in a hospital or outpatient transfusion center.

Donated blood is thoroughly screened for infectious agents and other factors that may put you at risk. Although serious complications can happen, the procedure is considered safe.

Sometimes, illness can make it difficult for your body to produce healthy blood. Some conditions that may require transfusion therapy include:

Blood types

We have different blood types according to the antigens in our blood cells. There are four main blood groups: O, A, B, and AB.

Some also have a substance called Rh factor in our red blood cells. Those who have it are Rh positive, and those who don’t are Rh negative. This is why you hear blood type referred to as O positive (O+) or B negative (B-), for example. If you’re Rh positive, you can receive positive or negative blood. If you’re Rh negative, you can only receive Rh negative blood.

It’s important that the blood used in a transfusion works with your own blood type. If it doesn’t, your own antibodies will attack the new blood and make you sick.

People who have type O- blood are called universal donors because type O- blood is safe for almost everyone to receive. Type O- blood is used in emergency situations when there’s no time to test a person’s blood type.

People with type AB+ blood are called universal recipients because they can receive almost any type of blood transfusion.

Blood components

Even though we don’t all have the same blood type, our blood is made up of the same components. Blood consists of solid and liquid parts. The solid part contains red and white blood cells and platelets. Red blood cells transport oxygen. White blood cells help fight infection. Platelets help your blood clot.

The liquid part is called plasma. It contains water, proteins, and salts.

If you’re receiving transfusion therapy, you may only need certain parts of blood. For example, people with sickle cell disease may only need red blood cells. Someone with leukemia may require platelets transfusions.

Serious complications can occur if donor and patient blood aren’t compatible. You’ll need a simple blood draw, after which the sample will be sent for laboratory testing. Be sure to tell your doctor if you’ve had reactions in response to previous blood transfusions.

Tell your doctor if you take dietary supplements containing iron.

You may be asked to sign papers consenting to transfusion therapy.

If possible, ask questions prior to the day of the procedure. For example, you might want to find out if you can have a family member donate their blood for your transfusion. Extra costs and delays may be involved with this option, which you’ll also want to ask your doctor about.

Transfusion therapy can take place in a hospital or an outpatient center. If you don’t have a permanent IV, a line will be inserted into one of your blood vessels. Your provider will confirm your identity and cross-check the blood you are about to receive.

You may receive a mild medication, usually diphenhydramine (Benadryl) or acetaminophen (Tylenol), to reduce side effects. Your vital signs will be checked and monitored. Generally, you will be free to move around during the transfusion, as long as you are careful not to disturb the IV. Blood will flow from a bag into the line for one to four hours.

Most people are able to resume normal activities soon after the procedure. Ask your doctor for aftercare instructions specific to your condition.

It’s extremely important that compatible blood is used. If not, your immune system will attack the donor blood. This can be a life-threatening event.

Although there is some risk, strict precautionary measures decrease the risk of transmitting infection or disease. According to the Centers for Disease Control and Prevention, transmitting infection through blood transfusion is rare in the U.S.

Transfusion reaction

Some people have a transfusion reaction following the procedure. Symptoms are generally mild and may include:

  • back, chest, or muscle pain
  • chills
  • coughing, wheezing
  • fever
  • headache
  • hives
  • itching, rash
  • swelling

You may have a delayed transfusion reaction. This happens when side effects occur days or even weeks later. Sometimes this includes dark-colored urine.

Be sure to report even mild side effects to your doctor or nurse immediately. Medication taken prior to a transfusion can cut down on side effects.

Iron overload

Ongoing transfusion therapy can cause iron overload in some people. Excess iron is stored in your liver, pancreas, endocrine glands, and heart, and can damage vital organs. Careful monitoring can tell your doctor if your body is storing too much iron. Prescription medications called chelations can help your body get rid of iron.

While there are currently no man-made alternatives for human blood, there are some drugs that can help do the job of some blood parts. Erythropoietin is a medicine that helps your body make more red blood cells. This can decrease the frequency of blood transfusions for people with chronic conditions requiring this procedure.

During surgery, surgeons can sometimes collect and reuse blood a person loses. This procedure is called autotransfusion. This can also reduce the need for a blood transfusion from a donor.