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Blood Donation Process


Ravindra Sarode

, MD, The University of Texas Southwestern Medical Center

Last full review/revision Feb 2020| Content last modified Feb 2020
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Healthy people donate a small amount of their blood to be used for blood transfusions. People usually give 1 pint (about 450 milliliters, approximately less than 1/10th of the total amount of blood in the body) and often different components of the blood (see Blood Products) are separated and given to different people.

The entire process of donating whole blood (that is, blood with all component cells) takes about 1 hour. Blood donors must be at least 17 years old and weigh at least 110 pounds (50 kilograms). In addition, they must be in good health. Their pulse, blood pressure, and temperature are measured, and a blood sample is tested to check for low blood count (anemia). Donors are asked a series of questions about their health, factors that might affect their health, and countries they have visited. Certain conditions and factors can permanently or temporarily disqualify people from donating blood. Disqualifying factors typically are those that might make donation dangerous for the donor or risk transmitting a disorder to the recipient. The decision to accept or disqualify a donor can be complicated. The American Red Cross provides detailed information on their web site (see Blood Donation Eligibility Requirements).

Did You Know...

  • Very few disorders permanently disqualify people from giving blood.

  • Most people can eventually give blood even if they are disqualified at first because most conditions that disqualify donors are temporary.

  • Donated blood is tested for many infections, so the chance of getting a disease from donated blood is very small.


Some Conditions That Disqualify People From Donating Blood


Permanent or Temporary Disqualification


Participation in certain high-risk activities


This includes any positive test for HIV, ever.

High-risk activities include

  • Use of intravenous drugs (ever).

  • Engagement in sex for compensation (ever).

Activities that increase risk of HIV infection


The FDA has changed recommendations for certain other high-risk activities from permanent to temporary (for up to 12 months) disqualification from last such activity. Activities include

  • Men who have sex with men (MSM) and women who have sex with MSM.

  • Sexual contact with a person who has ever had a positive HIV test, ever engaged in sex for compensation, or ever used IV drugs.

Anemia (a low level of hemoglobin in the blood)


People can donate blood after the anemia resolves.

Asthma, severe


Bleeding disorders, congenital


Cancers involving blood cells (for example, leukemia, lymphoma, or myeloma)


People cannot donate even if they are cancer-free.

Cancers, other


People may donate if they are cancer-free and treatment was completed more than 12 months previously.

People with mild, treatable forms (such as small skin cancers) may be able to donate before 12 months.

Drugs (some), such as acitretin, dutasteride, etretinate, finasteride, and isotretinoin


How long people have to wait depends on the drug.

Most drugs do not disqualify people from donating blood.

Heart disease, severe


Hepatitis, illness


People who have ever had hepatitis due to a virus cannot donate blood.

Hepatitis, exposure to


People must wait 12 months after possible exposure (for example, living with or having sex with a person with hepatitis, being incarcerated in a correctional facility for more than 72 hours, or having a human bite that broke the skin).


People can donate after their blood pressure is controlled.

Possible exposure to prion diseases, such as variant Creutzfeldt-Jakob disease (also called mad cow disease)


Exposure may occur when

  • People have used insulin derived from cows.

  • People have spent time in Europe since 1980 (ranging from more than 3 months to 5 years, depending on the country)

  • U.S. military personnel who lived on bases in Europe for more than 6 months during 1980–1996.

Malaria or exposure to malaria


People must wait 1–3 years.



Women must wait 6 weeks after giving birth.

Major surgery if recent




People must wait 12 months.


Temporary or permanent

People who received a transfusion in the United States must wait 12 months.

People who received a transfusion in the United Kingdom since 1980.

Vaccines (some)


How long people have to wait depends on the vaccine.


For recent Zika virus infection, the U.S. FDA recommends a 120-day deferral from resolution of symptoms or the last positive test, whichever is longer.

The FDA no longer recommends screening donor for risk factors; instead, all donor blood is to be tested for the Zika virus.

FDA = Food and Drug Administration; HIV = human immunodeficiency virus.

Generally, donors are not allowed to give blood more than once every 56 days. The practice of paying donors for blood has almost disappeared because it encouraged needy people to present themselves as donors and then sometimes to deny having any conditions that would disqualify them.

A person who is deemed eligible to donate blood sits in a reclining chair or lies on a cot. A health care worker examines the inside surface of the person's elbow and determines which vein to use. After the area immediately surrounding the vein is cleaned thoroughly, a needle is inserted into the vein and temporarily secured with a sterile covering. A stinging sensation is usually felt when the needle is first inserted, but otherwise the procedure is painless. Blood moves through the needle and into a collecting bag. The actual collection of blood takes only about 10 minutes, but the whole process from health history to a brief recovery period takes about an hour.

The standard unit of donated blood is about 1 pint (about 450 milliliters). Freshly collected blood is sealed in plastic bags containing preservatives and an anticlotting compound. A small sample from each donation is tested for some infectious organisms.

Testing Donated Blood for Infections

Blood transfusions can transmit infectious organisms carried in the donor's blood. That is why health officials have restricted blood donor eligibility and made blood testing thorough. All blood donations are tested for infection with the organisms that cause viral hepatitis, AIDS, selected other viral disorders (such as Zika virus and West Nile virus), Chagas disease, and syphilis.

Acquired immunodeficiency syndrome (AIDS)

In the United States, donated blood is tested for the human immunodeficiency virus (HIV), the cause of AIDS. The test is not 100% accurate because it will not be positive during the first few weeks after a person has acquired HIV infection. However, potential donors are interviewed as part of the screening process. Interviewers ask about risk factors for AIDS—for instance, whether the potential donors or their sex partners have injected drugs or had sex with a man who has male sex partners. Because of the blood test and the screening interview, the risk of contracting HIV infection through a blood transfusion in the United States is extremely low—1 in 1,500,000 to 2,000,000 according to recent estimates.

Viral hepatitis

Donated blood is tested for infection with the viruses that cause the types of viral hepatitis (types B and C) that are transmitted by blood transfusions.

These tests cannot identify all cases of infected blood, but with the rigorous testing and donor screening procedures, a transfusion poses almost no risk of transmitting hepatitis C. The current risk is less than 1 infection for every 2,000,000 units of blood transfused in the United States.

Hepatitis B remains the most common potentially serious disorder transmitted by blood transfusions, with a current risk of about 1 infection for every 1,000,000 units of blood transfused in the United States.


Blood transfusions rarely transmit syphilis. Not only are blood donors screened and donations tested for the organism that causes syphilis, but the donated blood is also refrigerated at low temperatures, which kills the infectious organisms.

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