FAQs About Blood and Blood Donation

About the Donation Process

How much blood is taken?

For a whole blood donation, approximately 0.5 L of blood is collected. For donations of other blood products, such as platelet or plasma, the amount collected depends on your height, weight and platelet count.

Are the history questions necessary every time I donate?

Yes, since this helps to ensure the safest possible blood supply. All donors must be asked the screening questions at each donation. Both AABB and FDA regulations specifically require that all blood donors complete the donor history questionnaire on the day of donation and prior to donating.

If you are a frequent blood donor, you may qualify to use an abbreviated Donor History Questionnaire. Ask if this option is available at your blood donor center and whether you qualify to use it.

Can I donate blood if I am taking a medication to prevent HIV?

All donors who have taken a medication to prevent HIV infection – known as pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP) – are temporarily deferred from blood donation due to the suppressive effect that these medications have on HIV testing. The duration of the deferral period varies. This waiting period is necessary because these medications can make HIV undetectable when donors are tested for HIV. AABB has developed PrEP/PEP FAQ resources for blood collectors and the public to provide additional information about these medication deferrals.

What does the term “donor deferral” mean?

Donor deferral means that an individual is not eligible to donate based on the current requirements. This waiting period is necessary to protect the health and safety of both the donor and the patient who receives the donated blood.

In the United States, blood collectors follow donor eligibility criteria based on requirements of the Food and Drug Administration, AABB Standards, and their own local policies. The medical director of the blood donor center has ultimate authority to establish a more stringent deferral policy based on their clinical judgement as a physician.

The period of time a person will not be eligible to donate depends on the specific reason for deferral. After the deferral period ends, a donor can return to the blood donor center to be reevaluated and resume donation if all donor eligibility criteria are met.

AABB’s donor deferral resource explains some of the most common reasons for deferral. Contact your local blood collector for specific questions about your eligibility.

If I was deferred once before, am I still ineligible to donate?

Your blood donor center will inform you if you are permanently deferred or temporarily deferred. The deferral time depends upon the reason for deferral. Prior to each donation, you will be given a mini-physical and medical interview. At that time, it will be determined if you are eligible to donate blood on that day.

If I just received a flu shot, can I donate blood?

Yes. There is no waiting period to donate after receiving a flu shot.

If I have a cold or the flu, can I donate blood?

No, blood centers require that you be in good health (symptom-free) and feeling well.

Can I still donate if I have high blood pressure?

Yes, if your blood pressure falls within the limits set by FDA regulations.

What if I'm taking aspirin or medication prescribed by my doctor?

Your blood donor center can best answer your questions. We recommend that you call the blood donor center ahead of time to inquire about any medications you are taking. Aspirin and ibuprofen will not affect a whole blood donation. However, apheresis platelet products can be affected if aspirin or aspirin products are taken 48 hours prior to donation. Many other medications are acceptable.

How long will the actual donation process take?

The entire donation process, from registration to post-donation refreshments, takes about one hour. The actual donation takes about 5-10 minutes.

Where is blood donated?

There are many places where blood donations can be made. Bloodmobiles (mobile blood drives on specially constructed buses) travel to many locations, making it easy for people to donate blood. Many people donate at blood drives at their places of work or at high schools, colleges, churches and other community organizations. People also can donate at community blood centers and hospital-based donor centers. You may use the online Locator to locate a nearby blood center or hospital to donate.

What is apheresis?

Apheresis, an increasingly common procedure, is the process of removing a specific component of the blood, such as platelets, red blood cells, plasma (liquid part of the blood) or granulocytes (white blood cells) and returning the remaining components to the donor. This process allows more of one particular part of the blood to be collected than could be separated from a unit of whole blood.

The apheresis donation procedure takes longer than that of a whole blood donation. A whole blood donation takes about 20 minutes to collect the blood as compared to an apheresis donation which may take about one to two hours, depending on the blood component(s) that is being donated.

What can you do if you aren't eligible to donate?

While a given individual may be unable to donate, he or she may be able to recruit a suitable donor. Blood banks are always in need of volunteers to assist at blood draws or to organize mobile blood drives. In addition, monetary donations are always welcome to help ensure that blood banks can continue to provide safe and adequate blood to those in need.

About Blood

What types of tests are performed on donated blood?

After blood is drawn, it is tested for ABO group (blood type) and Rh type (positive or negative), as well as for any unexpected red blood cell antibodies that may cause problems for the transfusion recipient. Blood is tested for:

  • Hepatitis B virus
  • Hepatitis C virus
  • HIV-1 and HIV-2
  • HTLV-I and HTLV-II
  • Syphilis
  • West Nile virus
  • Trypanosoma cruzi, the infectious agent causing Chagas' disease
  • Babesia – in states where testing is required by FDA guidance

Does donated blood stay on the shelf indefinitely until it is used?

No. Each unit of whole blood is separated into several components. Red blood cells may be stored under refrigeration for a maximum of 42 days, or frozen for up to 10 years. Platelets are stored at room temperature and may be kept for a maximum of five to seven days. Fresh frozen plasma is kept in a stored frozen state for up to one year. Cryoprecipitated AHF is stored frozen for up to one year. Granulocytes must be transfused within 24 hours of donation.

Other products manufactured from blood include albumin, immune globulin, specific immune globulins, and clotting factor concentrates. Commercial manufacturers commonly produce these blood products.

Why are there often blood shortages?

Most blood centers strive to maintain an optimum inventory level of a three-day supply. Due to unpredictable demands, the inventory often fluctuates hourly. When the blood supply drops below a three-day level, blood centers begin alerting local donors to increase the inventory to a safe operating level.

Is there such thing as artificial blood?

Scientists have yet to find a successful substitute for human blood. This is why blood donors are so vital to the lives of those who are in need of blood.

Who needs blood?

The need for blood is great. Every day in the U.S., approximately 29,000 units of red blood cells are required in hospitals and emergency treatment facilities for patients with cancer and other diseases, for organ transplant recipients, and to help save the lives of accident/trauma victims. In addition, nearly 5,000 platelet units and 6,500 units of plasma are also needed. In 2017, nearly 16 million blood components were transfused. With an aging population and advances in medical treatments and procedures requiring blood transfusions, there is always a need for blood and blood components.

What is the most common blood type?

The approximate distribution (%) of blood types in the U.S. blood donor population is as follows.*

Race or ethnicity









White non-Hispanic


















Black non-Hispanic


















North American Indian









All donors









*Garratty G, Glynn SA, McEntire R; Retrovirus Epidemiology Donor Study. ABO and Rh(D) phenotype frequencies of different racial/ethnic groups in the United States. Transfusion. 2004 May;44(5):703-6. doi: 10.1111/j.1537-2995.2004.03338.x. PMID: 15104651.

In an emergency, anyone can receive type O red blood cells. Therefore, people with type O blood are known as "universal donors." In addition, individuals of all types can receive type AB plasma.

What fees are associated with blood?

While donated blood is free, there are significant costs associated with collecting, testing, preparing components, labeling, storing and shipping blood; recruiting and educating donors; and quality assurance. As a result, processing fees are charged to recover costs. Processing fees for individual blood components vary considerably. Processing fees for one specific component also may vary in different geographic regions. Hospitals charge for any additional testing that may be required, such as the crossmatch, as well as for the administration of the blood.

What is the “availability of blood”?

Blood availability refers to the overall supply nationally or regionally. The blood supply varies among the many regions throughout the U.S. The blood supply level also fluctuates throughout the year. Factors impacting blood inventories often include holidays/travel schedules, inclement weather and illness, such as the outbreak of COVID-19. Historically, blood collections can be slow during the winter and summer months. A reduction in donor turnout rapidly impacts our nation's blood inventory.