Portrait of young woman wearing a protective mask laying in recliner chair receiving a blood transfusion

World Blood Donor Day

Every two seconds someone in the U.S. needs blood. And according to the American Red Cross, a single donation can save up to three lives.

On June 14, the National Heart, Lung, and Blood Institute (NHLBI) joins the World Health Organization (WHO) in observing World Blood Donor Day.

Simone Glynn, M.D., M.P.H., chief of the Blood Epidemiology and Clinical Therapeutics Branch in NHLBI’s Division of Blood Diseases and Resources, and Shimian Zou, Ph.D., a senior scientific officer for international blood science and an HIV/AIDS program coordinator there, answer questions about donating blood, the safety and availability of the blood supply, and ongoing research.

Blood Donor Basics

Q: Why is blood so important?

A: Blood forms in bone marrow, specifically in the tissues of certain bones, and healthy adults have about 5 to 6 liters of it circulating throughout their body. Each drop of blood contains red blood cells, white blood cells, platelets, and plasma.

When everything is working well, blood helps deliver oxygen and nutrients to cells, while moving waste to your liver and kidneys. This ongoing process is what keeps us alive.

Q: Who needs a blood donation?

A: Patients in need rely heavily on the many people who give blood. This includes patients who experience heavy bleeding and need critical care, such as people who’ve been in accidents. They need blood fast. Other people with blood disorders, which can alter how blood is produced or functions, may also need blood transfusions.

Blood donors come from a variety of people and they are real heroes. We like to say they’re giving the “gift of life.”

Q: Who can donate blood?

A: Generally, most people – about six in 10 – can donate blood. Volunteers should be in good health, be at least 16 or 17 years old, depending on the state they live in, and weigh at least 110 pounds. They should also have healthy levels of hemoglobin. Healthy red blood cells use hemoglobin (which uses the mineral iron) to deliver oxygen to cells.

Q: Why is donating blood so important?

A: Donating blood is always important because blood is perishable.

Platelets, for example, which help with clotting and can benefit cancer patients, can only be stored for 5 to 7 days. Red blood cells, which can benefit people with blood conditions that cause anemia, can be stored for up to 42 days. Plasma can be frozen and stored for up to a year, which can help patients with serious burns, shock, and bleeding disorders.

Blood transfusions may contain whole units of blood or be separated into components – like red blood cells, platelets, or plasma – based on each patient’s needs.

COVID-19 Pandemic and Blood Safety

Q: How has donating blood changed in the U.S. throughout the pandemic?

A: Early in the pandemic the Food and Drug Administration (FDA) issued COVID-19 safety protocols to keep blood donors and transfusion recipients safe. People can donate blood after they have had COVID-19 – but a waiting period determined by the FDA ensures that the blood donation is safe. 

Additionally blood donation centers use safety measures, such as mask wearing as appropriate (per guidance from the Center for Disease Control and Prevention), physical distancing (spacing between beds), sanitation, and ventilation, to mitigate the risk of spreading COVID-19 onsite.

Q: How safe is it to donate blood during the COVID-19 pandemic? 

A: As long as the safety protocols are followed for COVID-19, donating blood is safe for blood donors. 

Q: What about the safety of the blood supply during the COVID-19 pandemic?

A: NHLBI researchers looked into this question by studying blood samples from six major U.S. metropolitan regions between March and September 2020. After testing blood samples – representative of 257,809 single donations – for SARS-CoV-2, the virus that can cause COVID-19, the researchers found that the likelihood of a person receiving a blood donation with trace amounts of SARS-CoV-2 was .001% – a little over 1 in 100,000. Other studies conducted in Korea, France, and China have not found any cases of COVID-19 that were acquired from a blood transfusion. 

The take-home message from this study and others is that getting COVID-19 from a blood donation is insignificant compared to airborne transmission.

Blood Donations

Q: How are blood donations used throughout the world?

A: In developed nations like the U.S., the WHO found that the majority of blood transfusions help older adults. This may include adults who are having cardiovascular surgery, receiving an organ transplant, recovering from trauma, or dealing with cancer. Additional reasons people may need blood is for a blood disease, infectious disease, or gastrointestinal disease.

In developing countries, about half of all blood transfusions go to women with pregnancy complications or to young children with severe anemia – for example children with sickle cell disease or who are suffering from malaria.

Studying Blood Donations and How They Are Used

Q: What kinds of studies of blood are being done?

A: At NHLBI, the Division of Blood Diseases and Resources gives grants and other support to investigators who conduct research to improve the safety and availability of the global blood supply. To help with this effort, NHLBI supports two large research programs. One is called Recipient Epidemiology and Donor Evaluation Study (REDS). REDS works not only to improve blood safety and access, but also the safety and effectiveness of blood transfusion therapies. And it’s positioned to work fast in emergencies – such as COVID-19.

The other NHLBI research program is called BLOODSAFE. It was launched last year to enhance the availability and delivery of safe blood for patients from low or lower-middle income countries in Sub-Saharan Africa. Two groups that need particular attention, for example, are children with malaria or sickle cell disease and pregnant women who suffer from obstetric hemorrhage.

Q: How are blood donors helping scientists with this research?

A: The research could not be done without blood donors consenting to provide their information or blood for research. For example, scientists are studying blood donor samples to answer many COVID-19 questions, including: How long does immunity last?

Blood donations from several blood banks are helping researchers conduct this study, which will assess COVID-19 immune responses within 9 months of infection.

To learn more, visit:

Blood donations: https://nhlbi.nih.gov/health-topics/blood-donation
Blood research: https://redsivp.com/covid-19/
Blood disorders and blood safety: https://nhlbi.nih.gov/science/blood-disorders-and-blood-safety