Patient Information

Blood donation and transfusion

Blood donation and transfusion
Steven Kleinman, MD
Section Editor
Arthur J Silvergleid, MD
Deputy Editor
Stephen A Landaw, MD, PhD
Last literature review version 19.3: Fri Sep 30 00:00:00 GMT 2011 | This topic last updated: Thu Sep 29 00:00:00 GMT 2011 (More)

INTRODUCTION — 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 bank can describe the criteria for being a blood donor. The websites at the end of this topic also include information about eligibility criteria (see ‘Where to get more information’ below). People who have a pre-existing medical condition may wish to consult their own healthcare provider.

SCREENING MEASURES TO PROTECT THE DONOR — 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. In general, people with heart disease, heart valve conditions, irregular heartbeat, disease of the blood vessels in the brain, heart failure, and certain lung conditions are not allowed to donate blood unless this has been cleared with their healthcare provider.
  • Other medical conditions — Potential donors are asked if they feel healthy and well on the day of donation.
  • 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.


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, very high or very low heart rate (with the exception of highly conditioned athletes and those on beta blocker medication), or an irregular heart beat 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 or iron deficient after they donate. Individuals with hemoglobin levels that are too low are temporarily not permitted to donate blood. (See “Patient information: Anemia caused by low iron”.)


Time interval until next donation — Donors are eligible to donate no sooner than 56 days after their previous donation. However, this minimum interval can vary, depending upon how rapidly the person’s body is able to replenish their 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.

APHERESIS DONATION — A technology called apheresis has made it possible to collect specific components of blood during the donation procedure. 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).

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  • 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 MEASURES TO PROTECT THE RECIPIENT — Screening of blood donors helps to ensure that the donated blood is safe for transfusion into a recipient. A variety of different measures 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 potential or actual HIV infection, including questioning the donor about any signs or symptoms of HIV and behaviors that increase the risk of HIV.

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; 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

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) are permanently disqualified from donating blood.
  • 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 or a body piercing are not permitted to donate blood for 12 months. In other states, where these industries are carefully regulated by state law to ensure that the procedures are sterile, earlier donation may be permitted without the need for any waiting period.


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.

  • Creutzfeldt-Jakob disease (CJD) and variant CJD — 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.


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 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, usually two to five years.

    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 Food and Drug Administration (FDA). There is no risk of transmitting this condition to the recipient. (See “Patient information: Hemochromatosis (hereditary iron overload)”.)


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, five drugs are known to cause birth defects and are considered during donor screening:


  • Etretinate (Tegison®), used for severe psoriasis
  • Acitretin (Soriatane®), also used for severe psoriasis
  • Isotretinoin (Amnesteem, Sotret, Claravis, formerly known as Accutane®), used for severe acne
  • Finasteride (Propecia®, Proscar®), used for benign prostatic hypertrophy and hair loss
  • Dutasteride (Avodart®, Jalyn®), usually given for prostatic enlargement


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; 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 warfarin (Coumadin®) are generally not allowed to donate blood for approximately seven days after the last dose. The reason for this is that this blood does not contain sufficient quantities of clotting factor.

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, in most areas, Chagas disease. (See “Patient information: West Nile virus infection”.)

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 after donating (such as symptoms of upper respiratory tract infection or gastrointestinal illness). Such reports will be evaluated, and the unit of blood may be destroyed.

RISK OF INFECTION FROM A TRANSFUSION — 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-cell lymphoma/leukemia virus (HTLV)


AUTOLOGOUS BLOOD DONATION — Autologous blood donation is when a donor donates blood for themselves 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.

POTENTIAL COMPLICATIONS OF BLOOD DONATION — 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.

WHERE TO GET MORE INFORMATION — 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 every four months on our website (

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:

Patient information: Anemia caused by low iron
Patient information: Hemochromatosis (hereditary iron overload)
Patient information: West Nile virus infection

Professional Level Information:

Blood donor medical history
Clinical use of plasma components
Compatibility testing
Controversial areas in preoperative autologous blood donation
Directed (designated) blood donation programs
General principles of home blood transfusion
Immunologic blood transfusion reactions
Indications for red cell transfusion in the adult
Intraoperative and postoperative blood salvage
Laboratory testing of donated blood
Leukoreduction to prevent complications of blood transfusion
Massive blood transfusion
Preoperative autologous blood donation
Procedures used for blood donor screening: Protection of potential blood donors and recipients
Use of red blood cells for transfusion

The following organizations also provide reliable health information.


  • National Library of Medicine




  • National Heart, Lung, and Blood Institute




  • American Red Cross




  • America’s Blood Centers




  • AABB (formerly the American Association of Blood Banks)





  1. AABB Uniform Donor History Questionnaire file:// (Accessed on September 28, 2011).
  2. Dodd RY, Notari EP 4th, Stramer SL. Current prevalence and incidence of infectious disease markers and estimated window-period risk in the American Red Cross blood donor population. Transfusion 2002; 42:975.
  3. Whittaker S, Carter N, Arnold E, et al. Understanding the meaning of permanent deferral for blood donors. Transfusion 2008; 48:64.
  4. Orton SL, Virvos VJ, Williams AE. Validation of selected donor-screening questions: structure, content, and comprehension. Transfusion 2000; 40:1407.