A Third of Americans Don’t Know Their Blood Type. Here’s How to Learn Yours

Fact checked by Nick Blackmer

• Nearly a third of Americans don’t know their blood type.

• Experts say that knowing your blood type can be useful during an emergency or when you're donating blood to others.

• Blood tests, blood donations, at-home testing kits, and saliva tests can all tell you what your blood type is, but some options are more reliable (and affordable) than others.

According to a survey sponsored by USANA and conducted by OnePoll, about a third of Americans don’t know what their blood type is. However, experts say that number might be even higher.

“Probably more than half of people don’t know their blood type,” Donald Karcher, MD, FCAP, president-elect of the College of American Pathologists, told Verywell. “Most people just haven’t gotten that information or didn’t think of it as something that was important to have.”

If you don’t know your blood type but you know you should, how can you find out what it is? And what does it mean for your health if you’re A, B, AB, and Rh-positive or negative?

Here’s everything you need to know about learning what your blood type is and why having that information could be life-saving not just for you, but for others.

Learn More:How Blood Typing Works

Why Should You Know Your Blood Type?

Karcher said that knowing your blood type can help you understand your general health, but it’s also critical information to have in specific situations—for example, if you get in an accident and need an emergency blood transfusion.

There are also some more common situations where healthcare providers need to know your blood type. For example, if you need surgery (which carries a risk of losing blood and needing it replaced) or if you plan to get pregnant (in which case your blood type might not match up with the fetus’s).

Knowing your blood type isn’t just relevant to your health—it also matters if you’re donating blood to help other people, especially in communities where blood supplies are in short supply.

Learn More:What Blood Type Can Receive Any Blood?

What Are the Different Blood Types?

Majid Basit, MD, a cardiologist with Memorial Hermann in Houston, told Verywell that blood types are determined by the presence or absence of certain proteins on the red blood cells.

There are four main blood types: O, A, B, and AB. The letters stand for different proteins (antigens) in the blood. There is also another kind of antigen called Rhesus (Rh) factor, which is noted with a plus (+) or minus (-) sign depending on whether your blood has it or not.

When you talk about your blood type, you’ll say something like “A positive” if you’re type A and Rh factor positive or “A negative” if you’re type A and Rh factor negative.

Here are a few key facts about blood types:

• The most common blood type is O-positive.

• O negative is the universal donor. If you have O-negative blood, your blood does not have those antigens. Therefore, you’ll be popular at blood donation centers since your blood can be given to anyone in need (having no antigens means their body won’t see the blood as a threat and launch an immune attack). That can be lifesaving in an emergency when someone needs blood ASAP and there’s not enough time to type their blood.

• AB-positive is the universal recipient. If you’re AB-positive, you can get any blood type given to you because you have all the antigens. Since your immune system is familiar with them, you can get a type with any combination of antigens without it triggering your body to attack. While that’s very convenient, AB blood types are not common (in fact, the least common blood type is AB-negative).

All the letters and symbols can feel a little like high school algebra class, but the “alphabet soup” of blood typing matters. If you need a blood transfusion, you want to get blood that matches yours as closely as possible (or, at the very least, that your immune system will “play nice with” instead of attacking).

According to Basit, if someone gets the wrong blood type, “it can cause an allergic reaction which can sometimes be fatal.”

Only about 50 people in the world have “Rh-null” blood—which has no Rh factor. It’s also called “the golden blood type” because it’s so rare.

You might think it would be cool to have such a rare blood type, but people with it actually run into a lot of problems—especially if they are ever in a situation where they need a blood transfusion.

Learn More:How Blood Transfusions Save Lives

How to Learn Your Blood Type

If you have no idea what your blood type is, you’re not alone. But there are actually a few ways you can easily find out.

Ask Your Healthcare Provider

If you’ve been pregnant, received prenatal care, had surgery, or had another medical procedure done, it’s likely that your blood type was determined and put on record at some point.

According to Karcher, often the easiest way to find out your blood type is to just give your provider a call. In the era of electronic health records, it probably won’t take them long to track down your blood type if it’s on file.

If you have access to an online patient portal, you might be able to see your blood type when you log in. If you can’t get ahold of your provider or if they can’t find it, you can also try asking the hospital’s medical records department.

Get Blood Taken

Karcher said that a blood type test is not something that's routinely ordered, and it's not part of routine blood work. Usually, it's only done if a provider knows that a patient is either newly pregnant or going to have major surgery.

If you have some lab work coming up—for example, a routine test of your cholesterol levels—ask your provider if you can also find out your blood type at the same time.

If you’ve had your blood drawn before, Karcher said you can call the blood center or lab where you had it done to see if they have your blood type on record.

You can also ask about getting a blood type test through a local clinic or medical laboratory testing center like Labcorp or Quest Diagnostics.

Donate Blood

One of the most common ways to find out your blood type is to donate your blood to local blood banks or blood donation centers like the Red Cross.

When you give blood, you’ll usually get a donor card with information on how to access your blood type after your blood has been collected and tested.

If you’ve donated blood before, Karcher said that you can also reach out to your local blood donation center or laboratory testing center, as there’s a very good chance that information will be available.

Buy an At-Home Test

Basit said that you can buy an at-home blood test online to test your own blood at home and get the results in a few minutes. You can buy them from major medical laboratories like Labcorp and Quest Diagnostics or from brands like Everlywell.

Most at-home blood test kits come with a needle and testing card. Karcher said that while each kit has its own instructions, you will usually have to prick your finger and drop a little blood on a testing card that will give you a result.

For other tests, you might have to collect a few drops of your blood and ship it back to a laboratory for testing. In this case, you should get your blood type results a few days later.

However, Karcher added that there are some legal restrictions you might run into. In some states, you are not allowed to order a blood testing kit.

“I know that in New York, New Jersey, and Rhode Island, you are not able to do this test yourself,” said Karcher. “But, in most parts of the country, you could simply go online to any of the websites of these large laboratories, order the test, collect a sample, and get results.”

Hate Needles or Blood? Do a Saliva Test

If you’re afraid of needles or faint at the sight of blood, Karcher said there are saliva tests you can buy to learn your blood type, though they tend to be more expensive and may not be as accurate.

It might seem odd to test your spit to learn about your blood, but it works because both body fluids can have the same antigens—however, the operative phrase here is “can have.”

According to Karcher, only about 80% of people secrete the same antigens in their saliva that are in their blood. Therefore, Karcher said that saliva testing to learn your blood type may not be the best bet for the “20-plus % that may not be secretors.”

If you can get through the unpleasantness of pricking your finger to learn your blood type, Karcher said you’ll get the most reliable results.

Learn More:Can You Donate Blood to Yourself Before Surgery?

What’s the Best Way to Find Out Your Blood Type?

Both Karcher and Basit said that asking your provider for a blood test or donating blood to learn your blood type are your best bets. Not only are these methods more reliable than at-home tests, but they’ll cost you less or even be free (you don’t have to pay to donate blood!).

“By having a test done either in a laboratory, blood bank, or one of the large commercial laboratories, you’re getting the benefit of having the forward and reverse type done on that sample, which is a way to confirm the results,” said Karcher. “It’s not that at-home tests are not accurate, but the two-step test is one of the advantages of having this test done in a clinical laboratory or blood bank.”

If you don’t know your blood type, it’s pretty easy to find out and can be an important piece of information about your health to know. The best bet is to ask your provider if they have your blood type on file already. If not, they can order a test for you. You can also find out your blood type if you’re a blood donor, and that costs nothing.

While you can do some at-home tests to find out your blood type, you’ll have to front the cost for the kit and they’re not as reliable as the testing you provider can order or that blood banks do.

Read Next:How to Donate Blood Plasma