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• Posted March 25, 2026

'Universal Donor' Blood Supplies Dangerously Low, Study Warns

Blood banks are reporting dangerously low supplies of “universal donor” O-negative blood, a new study warns.

O-negative blood can be given to patients of any blood type, making it essential in medical emergencies where a person’s blood type is unknown, researchers said.

But O-negative supplies have dropped to critically low levels every year since 2019, researchers reported in the journal Anesthesiology Open.

Shortages have led the American Red Cross to offer $15 Amazon gift cards to anyone who donates blood through the end of March, researchers noted.

"O-negative blood is critical when patients need immediate transfusions before their blood type can be confirmed, such as during trauma care or other life-threatening emergencies," lead researcher Dr. Brent Lee said in a news release. Lee is director of clinical excellence and performance improvement with North American Partners in Anesthesia.

The problem is that demand for O-negative blood has grown while supply remains limited, researchers said.

About 13% of transfusions performed in 2023 involved O-negative blood, but only 7% of the entire U.S. population has O-negative blood, researchers reported.

Doctors are contributing to the problem by using O-negative blood in situations where other blood types could be used, the study found.

"Because anesthesiologists administer up to 60% of all blood transfusions in the United States, they play a key role in preserving and promoting responsible management of this scarce resource," Lee said.

The study argues that doctors should instead use O-positive blood, which is more readily available, for emergency transfusions in all male patients and for female patients who aren’t likely to become pregnant.

O-positive blood is called that because the blood cells are “positive” for the Rhesus factor D (RhD) antigen, which can trigger an immune response against the donated blood.

However, research has found that the risk of an immune response to an O-positive blood transfusion is “generally low” — around 3% to 6% of all cases — given that most people are RhD-positive, the study says. 

The exception is women with childbearing potential, as an RhD mismatch could be harmful to babies in future pregnancies, researchers said.

Because of that, O-negative blood should be saved for these women, as well as for people with O-negative blood, the study said.

The report also calls for performing blood typing as quickly as possible in medical emergencies so that patients can be switched off O-negative blood as soon as possible.

"In collaboration with other specialties and national organizations, anesthesiologists play a key role in alleviating chronic blood shortages and preserving the availability of O-negative blood for those who need it most," Lee said. "It is imperative that we maximize the benefits of blood transfusion, while strengthening the security of the nation’s blood supply."

More information

The American Red Cross has more about the U.S. blood supply.

SOURCE: American Society of Anesthesiologists, news release, March 19, 2026