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How Can You Find Out Your Blood Type?

type B blood sample

 

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Key Takeaways

  • Blood types are determined by unique proteins found on the surface of the red blood cells known as antigens.
  • Knowing your blood type is important if you need a blood transfusion, are pregnant or planning to become pregnant, or if you are going to be a transplant donor or recipient.
  • You can find out your blood type with a simple blood test, but it is not routinely ordered unless necessary.
  • Home blood type testing kits are easy to obtain and can provide results quickly, but they are for informational purposes only.

For most healthy people, blood type is just an interesting piece of information to have. But recent research exploring the link between blood type and COVID-19 risk may make it more top-of-mind than before. If you've ever donated blood or needed a blood transfusion, you may already know what your blood type is. But if not, there are a couple of ways to find out.

How Blood Type Is Determined

A lab test called a type and screen—sometimes referred to as blood typing—confirms a person’s blood type.

A type and screen test is not part of routine blood work, but you can still ask your doctor to perform this test if you're curious.

This blood test is most commonly ordered when:

  • A blood transfusion may be needed (prior to surgery, after trauma, or due to medical conditions and treatments that decrease blood production)
  • Workup is being completed for transplant recipients and donors
  • A patient is pregnant

What This Means For You

In a situation where a doctor needs to know your blood type for any reason, they will order a type and screen. Regardless of whether you already know your blood type, it will be screened again.

If you donate blood, you can request that the blood bank notify you of your blood type. Yvette Miller, MD, Executive Medical Director for the American Red Cross Donor and Client Support Center, tells Verywell that anyone who donates through the American Red Cross can create a donor account on The Red Cross Blood Donor app or online, and will be able to view their blood type under their profile.

Can You Use a Home Test Kit? 

At-home rapid blood type testing kits are available for those who are curious to know their blood type, but are for informational purposes only. They're widely available online, and can be found on Amazon or specialty home testing sites such as Everlywell.

Kits come with a lancet to prick the finger and a testing card to which the blood is applied. Results appear immediately.

While it may be intriguing to know your blood type, experts say there is little benefit to taking a home test to find out. In fact, 20% of home test users determine a result different from what a laboratory test shows.

"Home blood type testing kits are entertaining, but we can’t confirm how reliable they are,” Wesley Tait Stevens, MD, a board-certified pathologist who specializes in transfusion medicine at Riverside University Health System in California, tells Verywell via email. “Over the counter tests don’t have the same stringency as a diagnostic laboratory test."

What Are the Different Blood Types?

Your blood type is inherited from your biological parents and is determined by markers on your red blood cells also known as antigens.

There are eight possible blood types:

  • O negative
  • O positive
  • A negative
  • A positive
  • B negative
  • B positive
  • AB negative
  • AB positive

O negative is the universal blood type. In situations where blood type is unknown, anyone can receive O negative blood. Because of its high demand, there is often a shortage of O negative blood.

The letter associated with your blood type is based on three primary antigens found on red blood cells.

The two first antigens are called Type A and Type B. An individual who has both on his or her red blood cells will be Type AB. An individual who has neither A nor B antigens on his or her red blood cells will be Type O blood.

In addition to the Type A and Type B antigens, there is another antigen called the Rh factor. If the Rh factor is present on the red blood cells, the individual is Rh positive. If it is not present, the individual is Rh negative.

Rh factor is not really relevant to a person's health except after a woman's first pregnancy. Even then, there are only implications for the 15% of mothers who are Rh negative, involving potential damage to a baby's red blood cells in subsequent pregnancies. All pregnant women have their blood type, including Rh factor, tested.

For the vast majority of the population, blood type will not change during their lifetime, with few exceptions.

“Since blood is made in the bone marrow, the blood type can change if someone gets a bone marrow transplant,” Stevens says. ”Also, it may look temporarily different if a patient gets a large blood transfusion, such as from an emergency group O transfusion following a major trauma."

Why Does Blood Type Matter?

According to the American Red Cross, someone in the U.S. needs a blood transfusion every 2 seconds.

“Much of modern medicine relies on blood donation, so blood donation is very important,” Stevens says. “All blood types are needed in various ways, so knowing your blood type can help you know what donations would be most helpful.”

Miller emphasizes that there is a significant need for Black blood donors.

"African American individuals have a unique set of antigens that are not found in the Caucasian population, which makes up the majority of donors," she says. "There are some known incompatibilities and there is a struggle to have enough blood to meet the needs of African American community."

Sickle cell anemia is most common among Black and African Americans, and often requires blood transfusion.

COVID-19 has also affected the Black community disproportionately to the rest of the U.S. population—the mortality rate of Black people is 2.4 higher than that of white people —so there is an even higher need for Black donors right now.

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Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Time of Care Online Medical Notebook. The Difference between a Type and Screen and a Crossmatch.

  2. Bienek DR, Perez NM. Diagnostic accuracy of a point-of-care blood typing kit conducted by potential end usersMilitary Medicine. May 2013;178(5):588-592. doi:10.7205/MILMED-D-12-00500

  3. American Red Cross. Facts About Blood and Blood Types.

  4. American Red Cross. Why is Type O Blood so Important.

  5. American College of Obstetricians and Gynecologists. The Rh Factor: How It Can Affect Your Pregnancy.

  6. Centers for Disease Control and Prevention. Data & Statistics on Sickle Cell Disease. Updated October 21, 2019.

  7. The Atlantic. The COVID Tracking Project.