Blood Transfusion and Donation

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Possible risks of blood transfusions

Although blood transfusions can be life-saving, they are not without risks. Infections were once the main risk, but they have become extremely rare with careful testing and donor screening. Transfusion reactions and other non-infectious problems are now more common.

When you are getting a transfusion of any kind, it’s very important that you let your nurse know right away if you notice any changes in how you feel, such as itching, shivering, headache, chest or back pain, throat tightness, nausea, dizziness, trouble breathing, or other problems. You should report any that happen in the next few days, too.

Transfusion reactions

Blood transfusions sometimes cause transfusion reactions. There are several types of reactions and some are worse than others. Some reactions happen as soon as the transfusion is started, while others take several days or even longer to develop.

Many precautions are taken before a transfusion is started to keep reactions from happening. The blood type of the unit is checked many times, and the unit is cross-matched to be sure that it matches the blood type of the person who will get it. After that, both a nurse and blood bank lab technician look at the information about the patient and the information on the unit of blood (or blood component) before it’s released. The information is double-checked once more in the patient’s presence before the transfusion is started.

Allergic reaction

This is the most common reaction. It happens during the transfusion when the body reacts to plasma proteins or other substances in the donated blood. Usually the only symptoms are hives and itching, which can be treated with antihistamines like diphenhydramine (Benadryl). In rare cases these reactions can be more serious.

Febrile reaction

The person gets a sudden fever during or within 24 hours of the transfusion. Headache, nausea, chills, or a general feeling of discomfort may come with the fever. Acetaminophen (Tylenol) may help these symptoms.

These reactions are often the body’s response to white blood cells in the donated blood. They are more common in people who have had transfusions before and in women who have been pregnant several times. Other types of reaction can also cause fever, and further testing may be needed to be sure that the reaction is only febrile.

Patients who have had febrile reactions or who are at risk for them are usually given blood products that are leukoreduced (loo-ko-re-DUCED). This means that the white blood cells have been removed by filters or other means.

Transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a rare, but very serious transfusion reaction. It can happen with any type of transfusion, but those that contain more plasma, such as fresh frozen plasma or platelets, seem more likely to cause it. It often starts within 1 to 2 hours of starting the transfusion, but can happen anytime up to 6 hours after a transfusion. There’s also a delayed TRALI syndrome, which can begin up to 72 hours after the transfusion is given.

The main symptom of TRALI is trouble breathing, which can become life-threatening. If TRALI is suspected during the transfusion, the transfusion should be stopped right away.

Doctors now believe that several factors are involved in this illness, and medicines don’t seem to help. Many of the patients who get TRALI have had recent surgery, trauma, cancer treatment, transfusions, or have an active infection. Most of the time, TRALI goes away within 2 or 3 days if breathing and blood pressure are supported, but even with support it is deadly in 5% to 10% of cases. TRALI is more likely to be fatal if the patient was already very ill before the transfusion. Most often a patient will need oxygen, fluids, and sometimes support with a breathing machine.

Delayed TRALI has a higher risk of death, with one expert finding a death rate as high as 40%. If a patient who has had TRALI needs red blood cells, doctors may try to prevent future problems by removing most of the plasma from the red blood cells using a diluted salt water solution. Researchers are working on other ways to reduce this risk with careful donor selection and testing.

Acute immune hemolytic reaction

An acute hemolytic (he-mo-LIT-ik) reaction is the most serious type of transfusion reaction, but it’s very rare. It happens when donor and patient blood types do not match. The patient’s antibodies attack the transfused red blood cells, causing them to break open (hemolyze) and release harmful substances into the bloodstream.

Patients may have chills, fever, chest and lower back pain, and nausea. The kidneys may be badly damaged, and dialysis may be needed. A hemolytic reaction can be deadly if the transfusion is not stopped as soon as the reaction starts.

Delayed hemolytic reaction

This type of reaction happens when the body slowly attacks antigens (other than ABO antigens) on the transfused blood cells. The blood cells are broken down days or weeks after the transfusion. There are usually no symptoms, but the transfused red blood cells are destroyed and the patient’s red blood cell count falls. In rare cases, the kidneys may be affected, and treatment may be needed.

People don’t usually have this type of reaction unless they have had transfusions in the past. Those who do have this reaction need special blood tests before any more blood can be transfused. Units of blood that do not have the antigen that the body is attacking must be used.

Graft-versus-host disease

Graft-versus-host disease (GVHD) occurs when a person with a very weak immune system gets white blood cells in a transfused blood product. The white cells in the transfusion attack the tissues of the patient who got the blood.

This is more likely if the blood comes from a relative or someone who has the same tissue type (this is different from blood type) as the patient. The patient’s immune system doesn’t recognize the white blood cells in the transfused blood as foreign. This allows the white blood cells to survive and attack the patient’s body tissues.

Within a month of the transfusion, the patient may have fever, liver problems, rash, and diarrhea.

To prevent white blood cells from causing GVHD, donated blood can be treated with radiation before transfusion. (Radiation stops white blood cells from working but does not affect red blood cells.) These are called irradiated blood products. They are often used for people with cancer who might have weakened immune systems.


Blood transfusions can transmit infections caused by bacteria, viruses, and parasites. The chance of getting an infection from blood in the United States is extremely low, but the exact risk for each type of infection varies. Testing units of blood for germs that can cause infection has made the blood supply very safe, but no test is 100% accurate.

Bacterial contamination

Rarely, blood gets contaminated with tiny amounts of skin bacteria during donation. Platelets are the most likely blood component to have this problem. Because platelets must be stored at room temperature, these bacteria can grow quickly. (Other components are refrigerated or frozen.) Patients who get these platelets may develop a serious illness minutes or hours after the transfusion starts.

Blood banks routinely test platelets and destroy units of blood that are likely to cause harm. The tests are still being refined, but today fewer cases of illness are caused by platelets. Also, more hospitals use single donor platelets, which have a lower risk of bacterial contamination than pooled platelets.

Hepatitis B and C

Viruses that attack the liver cause these forms of hepatitis. Hepatitis is the most common disease transmitted by blood transfusions. A 2009 study on hepatitis B in donated blood suggested that the risk is about 1 in every 800,000 units or less. About 1 blood transfusion in 1.6 million may transmit hepatitis C.

Work continues to be done to reduce the risk of these infections even further. In most cases there are no symptoms, but hepatitis can sometimes lead to liver failure and other problems.

Several steps are routinely taken to reduce the risk of hepatitis from blood transfusion. People who are getting ready to donate blood are asked questions about hepatitis risk factors and symptoms of hepatitis. Donated blood is also tested to find hepatitis B virus, hepatitis C virus, and liver problems that could be signs of other types of hepatitis.

Human immunodeficiency virus

Human immunodeficiency virus (HIV) causes acquired immune deficiency syndrome (AIDS). Testing each unit of donated blood for HIV began in 1985, and all donated blood is now tested for HIV.

With improved testing for HIV, the number of transfusion-related AIDS cases continues to drop. The risk of HIV transmission from a transfusion is about 1 in 2 million. Along with testing, the risk is reduced by asking donors questions about HIV risk factors and symptoms.

Other infections

Along with the tests noted above, all blood for transfusion is tested for syphilis, as well as HTLV-I and HTLV-II (viruses linked to human T-cell leukemia/lymphoma). Since 2003, donated blood has been tested for the West Nile virus, too. In 2007, blood banks also began testing for Chagas disease (common in South and Central America).

Diseases caused by certain bacteria, viruses, and parasites, such as babesiosis, malaria, Lyme disease, and others can also be spread by blood product transfusions. But because potential donors are screened with questions about their health status and travel, such cases are very rare.

Last Medical Review: 10/07/2013
Last Revised: 10/07/2013