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

Steven Kleinman, MD
Section Editor
Arthur J Silvergleid, MD
Deputy Editor
Jennifer S Tirnauer, MD
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Blood is essential for transporting oxygen, nutrients, and other substances to tissues throughout the body. Donated blood can be lifesaving for individuals who have lost blood because of accidents or surgery, as well as for people who have become severely anemic or have dangerously low platelet counts because of certain medical conditions and/or treatments. Screening measures help to maximize safety of blood donation for the donor and the recipient.

For people who are considering donating blood, a local blood center can describe the criteria for being a blood donor. The websites at the end of this topic also include information about eligibility criteria, which may vary slightly between different blood centers (see 'Where to get more information' below). People who have a pre-existing medical condition may wish to consult their own healthcare provider.


Several screening measures are used to ensure that blood donation is safe for the donor and is unlikely to have any negative health effects.

Medical history interview — All blood donors are asked questions about their medical history to help determine whether they can safely donate blood without experiencing any negative health effects [1]. During the donation, one unit of blood (approximately 500 mL, or 17 fluid ounces) is removed.

Heart and lung disease – Potential donors are asked if they have ever had heart, lung, or blood diseases. People with heart disease, heart valve conditions, irregular heartbeat, disease of the blood vessels in the brain, heart failure, and certain lung conditions may be excluded from blood donation, or they may be allowed to donate blood provided this has been cleared with their healthcare provider and they have had no major symptoms in the prior six months.

Other medical conditions – Potential donors are asked if they feel healthy and well on the day of donation. A prospective donor should mention other serious medical conditions to the donor health historian who will then evaluate eligibility to donate.

Seizures – People with a history of seizures can donate blood, provided they have had no seizures within a certain period of time (usually one to six months).

Recent surgery – People who have undergone recent surgery are permitted to donate blood when healing is complete and they have resumed full activity. However, if a transfusion was given at the time of surgery, donation is not allowed for one year.

Pregnancy – Women who are pregnant are not permitted to donate blood during pregnancy and for six weeks after the pregnancy ends.

Age requirement – The minimum age for blood donation is 16 or 17 years, depending upon the state. When allowed, 16-year-olds must bring a signed permission form from a parent. In most cases, there is no upper age limit for donation, although approval from the donor's physician is required in some cases.

Weight requirement – Individuals weighing less than 50 kg (110 pounds) are not permitted to donate blood. The less a donor weighs, the greater the likelihood of having a reaction, such as dizziness and fainting following donation. Although reactions to blood donation are rare, individuals weighing between 50 and 54 kg (110 and 119 pounds) are most likely to experience reactions. Most blood centers perform an additional evaluation of donors aged 16 to 18 who are just over the weight limit, which takes into account the donor's estimated blood volume, calculated from the donor's height and weight. There is no upper weight limit for donating blood, although some centers have an upper weight limit based on the size/strength of the donor phlebotomy chair.

Questions are also asked that address the safety of the transfusion for the person receiving the blood. (See 'Screening measures to protect the recipient' below.)

Medical evaluation — In addition to a medical history, donors undergo a brief physical examination before donation to check for any obvious signs of illness or conditions that would disqualify them from blood donation.

Vital signs – The pulse, blood pressure, and temperature of a donor are checked before donation. Individuals with a fever, high blood pressure (generally higher than 180/100), very high or very low heart rate (with the exception of highly conditioned athletes and those on beta blocker medication), or an irregular heartbeat are temporarily not permitted to donate blood.

Blood test – A small blood sample is taken from a fingerstick and tested to check for the number of red cells or the amount of hemoglobin in the blood. This is done to ensure that the donor is not anemic or likely to become anemic after they donate. Individuals with hemoglobin levels that are too low are temporarily not permitted to donate blood. (See "Patient education: Anemia caused by low iron in adults (Beyond the Basics)".)

Time interval until next donation — Donors are eligible to donate no sooner than 56 days (eight weeks) after their previous donation. However, this minimum interval can vary, depending upon how rapidly the person's body is able to replenish its red blood cells. Some donors, especially women who have heavy menstrual periods, will not be able to donate every 56 days because their iron stores are not sufficient to replenish the lost red blood cells.

Donating blood removes iron from the body and this can result in iron deficiency in individuals who donate frequently, such as men of any age and women over 50 who donate three or more times per year, or women under age 50 who donate two or more times per year. Many blood organizations recommend that, in addition to eating foods rich in iron, people who donate this frequently take a multivitamin with iron or an iron-only supplement to replace the iron lost through each blood donation.


A technology called apheresis has made it possible to collect specific components of blood. Apheresis is used to selectively collect red blood cells, platelets (blood components that play an important role in clotting), plasma, and granulocytes (a type of infection-fighting white blood cell). The procedure is done in the blood center or at a blood drive and involves inserting a needle in a vein in each arm. Blood is withdrawn through one needle, passed through an apparatus that separates plasma from specific types of blood cells (platelets or red cells) and retains the desired component, and then the remainder of the blood is returned to the donor through the other needle. It takes from one to two hours.

Red blood cells – Donors can give red blood cells by apheresis once every 16 weeks. This is less frequent than whole blood donation because a greater amount of red blood cells are collected during the apheresis procedure.

Platelets – Donors can give platelets up to 24 times per year. Approximately 1 percent of people have a mild reaction to one of the substances (citrate) that is mixed with the blood during platelet donation; the reaction can include feelings of numbness and tingling, muscle cramping, and nausea. The reaction can be treated or prevented by taking a calcium supplement before or during the donation.

Granulocytes – Donors of granulocytes may be given granulocyte colony-stimulating factor (G-CSF) and/or a glucocorticoid medication called dexamethasone on the day before donation to increase the number of granulocytes in their blood. Glucocorticoids are usually not given to individuals who have diabetes, gastrointestinal ulcers, or glaucoma. The side effects of G-CSF and dexamethasone may include headache, joint pain, fatigue, insomnia, allergic reactions, and fever.


Screening of blood donors helps to ensure that the donated blood is safe for transfusion into a recipient. A variety of different measures, including self-reporting of infectious exposures and other infectious disease risk factors, and laboratory testing of the blood, are used for this screening.

Elimination of payment for donation – Since the late 1970s, volunteer donors have been the source of all whole blood and blood components in the United States. Donors are sometimes paid for donating plasma that is used to manufacture other blood products. However, to protect the recipient, these products undergo additional treatment to kill any infectious agents that might be in the product.

Screening for infections

Human immunodeficiency virus (HIV) — The human immunodeficiency virus (HIV) is the virus that causes AIDS. A variety of measures are used to screen donors for HIV infection or risk factors for HIV, including questions about any signs or symptoms of HIV and behaviors that increase the risk of HIV. Such behaviors include using non-prescription intravenous (IV) drugs, having sex with a prostitute or in exchange for money or drugs, and for men, having sex with another man. Depending on your answers to these questions, you may not be allowed to donate blood, or you may need to wait for a period of time before you are eligible. In December 2015, the guidelines for men who have sex with men were changed; rather than being ineligible to donate blood indefinitely, the wait period is now at least one year from the last sexual contact with another man.

People who want to be tested for HIV or other sexually transmitted infections should not donate blood for this purpose. Even though donated blood is tested for HIV, the tests are not perfect and there is a small possibility that a person who might have been exposed to HIV could transmit the virus to a recipient if they donate blood. Free and anonymous HIV testing is available elsewhere (see www.hivtest.org).

Hepatitis — Hepatitis is an infection that causes inflammation of the liver. Blood donors are routinely screened to determine whether they have or have been exposed to hepatitis.

People who have had viral hepatitis (A, B, or C) or hepatitis of unknown origin after their 11th birthday are permanently disqualified from donating blood.

People who have ever had a positive test for hepatitis B surface antigen (a marker for hepatitis B virus infection) are permanently disqualified from donating blood. Hepatitis B vaccination may temporarily cause this test to become positive [2]. In order to avoid being disqualified as a blood donor, a person who has recently received the hepatitis B vaccine should wait 21 days before donating blood. At that time, this test should be negative.

People who have had sexual contact or have lived in the same dwelling (eg, house, dormitory) with someone who has hepatitis (A, B, or symptomatic hepatitis C) are disqualified for 12 months after their last exposure to that person, depending upon the particulars of the exposure.

People who have received a blood transfusion are not permitted to donate blood for 12 months after the date of transfusion.

In some states, people who have received a tattoo are not permitted to donate blood for 12 months. In many other states, where the tattooing industry is carefully regulated by state law to ensure that the procedures are sterile, donation may be permitted without the need for any waiting period. With regard to ear or body piercing, donation is allowed if the procedure was performed with sterile or single-use equipment.

Parasitic diseases — Blood donors are routinely asked questions about possible exposure to several parasitic diseases that can be transmitted by blood transfusion.

Malaria – Transfusion-transmitted malaria is common in some parts of the world but is extremely rare in the United States. Donors who have had malaria are not permitted to donate for three years after they become free of symptoms. Travelers to regions where malaria occurs are not permitted to donate blood for one year after they leave the area, provided they have not had symptoms of malaria. Immigrants from or residents of countries where malaria is common are not permitted to donate for three years after their departure from that country. (Residency is usually defined as living in the country for at least five years.)

Chagas disease and babesiosis – Transmission of Chagas disease (American trypanosomiasis) by transfusion is rare in the United States. Blood donors are asked if they have ever had Chagas disease, and most donated blood is tested for Chagas disease.

Transmission of babesiosis (a malaria-like illness spread by ticks) by transfusion is uncommon. Blood donors are asked if they have ever had this disease. In areas where babesiosis is more common, blood may be tested for it

Prion diseases — Creutzfeldt-Jakob disease (CJD) is a rare but fatal neurologic disease. Variant Creutzfeldt-Jakob disease (vCJD) is a somewhat similar disease that first appeared in the United Kingdom (UK) in 1996. Affected individuals may have no symptoms of CJD or vCJD for many years. The infectious agent of both these diseases is an abnormally folded protein called a prion.

To date, there have been no reported cases of transfusion-related transmission of CJD and only four reports of probable transmission of vCJD in the UK. Despite this extremely small (vCJD) risk, donors who meet one or more of the following criteria are not allowed to donate:

Have spent ≥3 cumulative months in the UK from 1980 to 1996, or

Have spent ≥5 cumulative years in Europe from 1980 to present, or

As current or former US military personnel, civilian military employees and their dependents, have lived for ≥6 months at US military bases in Northern Europe from 1980 to 1990 or elsewhere in Europe from 1980 to 1996, or

Received a blood transfusion in the UK or France between 1980 to present, or

Injected bovine (from cows) insulin from the UK or other countries with a history of mad cow disease (bovine spongiform encephalopathy)

Bacterial infection — Bacteria can get into donated blood if a donor has a bacterial infection, if bacteria on the skin gets into the blood from the needle stick, or if there is a skin infection near the location where the blood is drawn. To reduce the likelihood of bacterial contamination of blood, the skin around the site is carefully examined and cleaned before the needle is inserted.

Donors who have a fever, who do not feel well, or who are taking oral antibiotics (except for acne) are not permitted to donate blood. These restrictions also apply to individuals who are banking blood for their own use (see 'Autologous blood donation' below).

Other infections — Donated blood cannot be tested for every possible infection, and new types of infections are frequently emerging around the world. Examples of such infections are Ebola virus and Zika virus. The pre-donation educational material given to donors, as well as the questionnaire, includes several general questions that are designed to identify individuals who either have infection symptoms or who have travelled to locations where these infections are more common (eg, possible exposure to Zika virus due to travel to certain countries). In addition, the blood center also informs donors that they should call the blood center if specific medical symptoms develop in the two weeks following donation; this is so the donated unit can be removed from the blood supply. However, questions in the pre-donation questionnaire are directed at general signs of infection, and individuals who might be at risk of transmitting an infection due to travel or behaviors are asked to "self-defer," which means to avoid donating blood. The decision to self-defer can be made at the time of donation or after the donation has been completed (in which case the center will not use or distribute the donated blood).

Other medical conditions — In order to protect the recipient against non-infectious complications, the donor is evaluated for certain medical conditions before blood donation.

Cancer – There have been no reported cases of the transmission of cancer by blood transfusion. However, because such transmission is theoretically possible, donors are screened for a history of cancer.

Donors who have had cancer of a solid organ or tissue (such as the lung, liver, breast) are permitted to donate if they have been symptom-free and cancer-free for a defined period of time off of treatment. This time period varies but is at least one year.

Donors who have had blood cancers (such as leukemia or lymphoma) are permanently disqualified from donating.

Donors who have had a superficial cancer that has been completely removed by surgery (such as basal cell cancer of the skin or early cervical cancer) can donate blood without any waiting period.

Hemochromatosis – Individuals with hereditary hemochromatosis (a condition in which frequent removal of blood is the standard treatment) can donate their blood for transfusion if they meet other criteria for being a donor and if the blood bank has met certain regulations from the US Food and Drug Administration (FDA). The acceptance of blood donations from these individuals has not been uniformly implemented, perhaps due to the costs of meeting regulations and removing financial incentives to blood donation. The FDA maintains a list of collection centers that accept these donations [3].

There is no risk of transmitting hemochromatosis to the recipient. (See "Patient education: Hemochromatosis (hereditary iron overload) (Beyond the Basics)".)

Recent vaccinations — There are strict standards for when you can donate blood after you have received a vaccination. When you go to donate blood, you will be asked if you have had any recent vaccinations. If you have, you might have to postpone your blood donation.

For some live or attenuated (weakened) viral or bacterial vaccines (measles, mumps, oral polio, oral typhoid, yellow fever), you have to wait at least two weeks before donating your blood. For rubella or varicella zoster vaccines, you have to wait four weeks.

Medications — Most medications taken by donors do not pose a risk to recipients. However, a number of drugs are known to cause birth defects and are considered during donor screening:

Etretinate (brane name: Tegison), used for severe psoriasis

Acitretin (brand name: Soriatane), also used for severe psoriasis

Isotretinoin (brand names: Absorbica, Amnesteem, Claravis, Myorisan, Zenatane; formerly known as Accutane in the United States), used for severe acne

Finasteride (brand names: Propecia, Proscar), used for benign prostatic hypertrophy and hair loss

Dutasteride (brand name: Avodart), usually given for prostatic enlargement

Vismodegib (brand name: Erivedge), used for basal cell skin cancer

Donors who have taken isotretinoin and finasteride are asked to wait one month after the last dose before donating blood; donors who have taken dutasteride are asked to wait six months; donors who have taken vismodegib are asked to wait seven months; and donors who have taken acitretin are asked to wait three years. Individuals who have taken etretinate are permanently disqualified from donating blood.

People who took aspirin or aspirin-containing medications within the previous 48 hours are allowed to donate whole blood but are not allowed to donate platelets by apheresis. People who took anti-platelet drugs (eg, clopidogrel [sample brand name: Plavix] or ticagrelor [sample brand name: Brilinta]) must wait a variable period ranging from 2 to 14 days to donate platelets by apheresis. People who took anti-clotting medications (also called "blood thinners") are generally not allowed to donate blood for a minimum of two or seven days (depending on the specific medication) after the last dose. Anti-clotting medicines include warfarin (sample brand name: Coumadin), dabigatran (brand name: Pradaxa), rivaroxaban (brand name: Xarelto), apixaban (brand name: Eliquis), and edoxaban (brand names: Savaysa, Lixiana). The reason for this is that the person who receives the blood may get some of the effect of the blood thinner.

Laboratory testing of donated blood — After a unit of blood has been donated, the blood is tested in a laboratory for infectious diseases that can be transmitted by blood transfusion. These include tests for HIV, hepatitis B, hepatitis C, human T-lymphotropic virus (HTLV), West Nile virus, syphilis, and Chagas disease. (See "Patient education: West Nile virus infection (Beyond the Basics)".)

Confidential unit exclusion (CUE) — The confidential unit exclusion (CUE) process allows someone who has donated blood to confidentially indicate that his or her blood should not be given to others. This process protects individuals who feel pressured to donate in the workplace or during community blood drives. Donors are asked to place a bar code sticker on their donation form, indicating if their blood should be used. This is done after the interview, but before donation. Although this procedure was commonly used in the past, most United States blood banks no longer use it.

Registry of deferred donors — A registry of deferred donors contains names of individuals who have been disqualified from blood donation in the past. Some donors in the registry have infectious diseases, such as hepatitis B or HIV infection. Theoretically, it is possible that an individual with one of these diseases could have a positive test result at one time but negative test results at a later time.

Other donors in the registry have provided information in the past that disqualified them from blood donation. A donor's name is usually checked against this registry before and after donation. The reason for the deferral is not usually available to staff at the collection facility.

Telephone callbacks — After donating blood, donors are given a phone number so that they can call the donation center to report any factors that may affect the use of their blood or to report symptoms of infections in the first days to two weeks after donating (such as symptoms of upper respiratory tract infection, gastrointestinal illness, or infection with a virus transmitted by mosquitos). Such reports will be evaluated, and the unit of blood may be destroyed.


Safety measures, such as improved screening tests, have dramatically reduced the risk of acquiring a viral infection from a blood transfusion. Recent estimates suggest the following risks of developing certain infections after receiving a unit of blood:

1 in 200,000 to 1 in 360,000 for hepatitis B

1 in 1 million to 1 in 2 million for hepatitis C

1 in 1.5 million to 1 in 2 million for human immunodeficiency virus (HIV)

1 in 2 million for human T-lymphotropic virus (HTLV)


In addition to the risk of infection from transfusion, other risks include the following:

Shortness of breath due to immune/inflammatory reactions, known as transfusion-associated acute lung injury (TRALI)

Shortness of breath due to the large volume of fluid, known as transfusion associated circulatory overload (TACO)

Allergic reactions to proteins and/or cells in the transfusion

Immune attack of the recipient by the transfused cells, also called transfusion-associated graft-versus-host disease (ta-GVHD)

Blood incompatibility, leading to destruction of the transfused cells by the recipient's immune system

Fever due to fever-causing hormones (cytokines) in the transfusion, also called febrile nonhemolytic transfusion reaction (FNHTR)

These risks occur infrequently and are well known to clinicians; measures are taken routinely in order to minimize them further.


Autologous blood donation is when a donor donates blood for her or himself several days to six weeks ahead of a scheduled surgery, when blood might be needed. Autologous blood donation reduces the risk of most, but not all, infectious complications of blood transfusion.


Most people who donate blood do not have any complications that require medical care. The most common complications include bruising or soreness at the needle site and fatigue.

A small percentage (2 to 5 percent) of people feel faint and/or pass out before, during, or after donating blood. This is more common the first time a person donates and in people who are younger. Drinking a 16-ounce (473 mL) bottle of water before donating may reduce this risk.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Blood donation (giving blood) (The Basics)
Patient education: Hemochromatosis (The Basics)
Patient education: Myelodysplastic syndromes (MDS) (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Anemia caused by low iron in adults (Beyond the Basics)
Patient education: Hemochromatosis (hereditary iron overload) (Beyond the Basics)
Patient education: West Nile virus infection (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Blood donor screening: Medical history
Clinical use of plasma components
Pretransfusion testing for red blood cell transfusion
Directed (designated) blood donation programs
General principles of home blood transfusion
Immunologic transfusion reactions
Indications and hemoglobin thresholds for red blood cell transfusion in the adult
Surgical blood conservation: Blood salvage
Blood donor screening: Laboratory testing
Leukoreduction to prevent complications of blood transfusion
Massive blood transfusion
Surgical blood conservation: Preoperative autologous blood donation
Blood donor screening: Procedures and processes to enhance safety for the blood recipient and the blood donor
Red blood cell transfusion in adults: Storage, specialized modifications, and infusion parameters

The following organizations also provide reliable health information [1,4-6]:

National Library of Medicine – www.nlm.nih.gov/medlineplus/healthtopics.html

National Heart, Lung, and Blood Institute – www.nhlbi.nih.gov/index.htm

American Red Cross – www.redcross.org

America's Blood Centers – www.americasblood.org

AABB (formerly the American Association of Blood Banks) – www.aabb.org

Literature review current through: Nov 2017. | This topic last updated: Fri Dec 23 00:00:00 GMT 2016.
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