Do you know what blood type you are? What about the blood type of everyone in your family?

I do, and I even know the blood type, or ketsuekigata 血液型 （ けつえきがた ） , of all my friends, too. And I'm not alone. According to a 2016 survey of 3,355 Japanese people, 99% knew their blood type.

Wow! But why all the blood knowledge?

血液型（けつえきがた） blood type

In Japan, blood types are considered an important indicator of a person's personality. It's known as the "Japanese Blood Type Personality Theory." Though this may seem far-fetched, a lot of people believe in it. In fact, the aforementioned survey shows 29% of males and 45% of females believe.

If you're planning on visiting Japan or interacting with Japanese people, read on. Understanding Japan's obsession with blood types can help you make new friends and fit in with Japanese groups. Plus, you'll find out where these beliefs came from and why it has such a hold on the Japanese consciousness.

Japanese Blood Type Personality Theory

Japan's interest in blood types comes from the idea that a person's blood helps define their personality. There are personality traits for each blood type. When someone acts a certain way, Japanese people like to tease, saying, "Of course you'd do that, you're B," and so on. It facilitates communication and helps people feel more open with one another.

Blood types also help Japanese people decide if they're good match, romantically or otherwise. Certain blood types pair well and promote better relationships, or so the thinking goes.

So when a Japanese person asks:

血液型 （ けつえきがた ） 、 何 （ なに ） 型 （ がた ） ？

、 ？ What blood type are you?

Don't freak out! No one is asking you to donate blood. The question merely expresses curiosity about you as a person. If you've ever been asked, "What's your sign?" in English, it's the same idea.

Now for the fun stuff! Want to find out if your personality matches your blood type? Take a look at the chart below to find out. And don't worry if you're positive or negative. That matters in medical situations, but doesn't affect you here.

Blood Type Ratio in Japan Positive Traits Negative Traits A 40% Earnest, Neat Stubborn, Anxious O 30% Easygoing, Leadership Ability Insensitive, Unpunctual B 20% Passionate, Creative Selfish, Uncooperative AB 10% Talented, Composed Eccentric, Two-faced

To get a clearer idea of how these blood type personalities play out, here's a picture from Twitter that demonstrates it well.

Mikan were peeled by four family members with different blood types

Mom, A: peeled the orange cleanly.

peeled the orange cleanly. The picture poster, AB: peeled artistic shapes.

peeled artistic shapes. Dad, B: peeled roughly and wrapped it around a used tissue.

peeled roughly and wrapped it around a used tissue. Younger brother, O: broke the peel into small pieces and made a mess.

This is just the tip of the iceberg though. Let's dive deep into these giant pools of blood. If you know your blood type, try and see how well these descriptions match you.

Blood Type A

Most of the Japanese population is type A. People with this blood type are described primarily as kichōmen 几帳面 （ きちょうめん ） , or well-organized. They like to keep things neat but can be stubborn and get stressed out easily. They also value harmony with others. Agricultural people are the root of blood type A, and it's been said working collaboratively on farms developed these blood type personality traits.

几帳面（きちょうめん） well-organized

Timid Mild-mannered Anxious Earnest Sensitive Stubborn Intense Reserved Patient Responsible Fastidious Tense Tactful Shy Withdrawn Polite Perfectionist Stressed Conscientious Wary Kind Diligent Attentive Composed Reliable Nervous Neat

Blood Type O

Blood type O is often described as rakkanshugi 楽観主義 （ らっかんしゅぎ ） , or optimistic. They are outgoing, have leadership abilities, and are able to set the mood for groups of people. They don't care much about little things (as you can see from the mikan picture above), so their behavior sometimes freaks out more sensitive A types. Though they're often late to events (and sometimes rude), O types are incredibly resilient and flexible, enabling them to roll with the punches.

楽観主義（らっかんしゅぎ） optimistic

Optimistic Easygoing Leadership Ability Insensitive Unpunctual Calm Confident Self-determined Strong-willed Intuitive Self-centered Cold Unpredictable Workaholic Outgoing Energetic Social Flexible Realistic Financially-minded Resilient Romanticist Cautious Devoted Peaceful Carefree Impressionable Insecure Emotional Ambitious Trendsetter Independent Loyal Athletic Robust Passionate Agreeable Arrogant Vain Jealous Ruthless Rude Imitator

Blood Type B

Blood type B is generally described as jikochū 自己中 （ じこちゅう ） , or selfish. They are also known for their creativity. Blood type B has a strong sense of curiosity, but at the same time, loses interest easily. Though there are a lot of positives to B types, people tend to focus on the negatives for reasons we'll get into later. Some say their root is in nomadic peoples who roamed from place to place.

自己中 （じこちゅう） selfish

Selfish Passionate Erratic Wild Active Uncooperative Creative Strong Irresponsible Unforgiving Relaxed Freewheeling Unconventional Unpretentious Pragmatist Flexible Curious Cheerful Outgoing Adventurous Indecisive Unpredictable

Blood Type AB

Blood type AB is a hybrid of A and B, two different personalities mixed together. They are often seen as dual-natured and complicated. For example, they are shy like A types, but also are outgoing like type B. Blood type AB is the rarest in Japan (and many other places in the world, too), so they are hard to find. This reinforces the stereotype that AB people are are kawarimono 変わり者 （ か もの ） , or eccentric.

変わり者（かわりもの） eccentric

Talented Composed Rational Artistic Aloof Cool Two-faced Controlled Sociable Critical Indecisive Forgetful Irresponsible Shy Outgoing Trustworthy Self-centered Sensitive Dream Chaser Spiritual Calm Mysterious Vulnerable Complicated Private Creative Eccentric Charming Impatient Proud Diplomatic Discriminating Popular Adaptable

Blood Type Personality Compatibility

You might be wondering which blood types get along with each other. Compatibility can differ depending on how the stereotypes are interpreted, so let's dig into how relationships work in the Japanese blood type personality theory.

A × A: These similar personalities generate empathy and affection, but sometimes create irritation because both people are so intense.

A × O: Type A and Type O have very different personalities (A is sensitive, but O is not). They cover each other's weaknesses, but the differences may stress them out.

A × B: Type A envies Type B's ability to enjoy things at their own pace. Type B is uncomfortable with A's doting. The kindness feels intrusive.

A × AB: This combination depends on the individuals. AB is part A and part B. Type A wouldn't get along with an AB who is too strong on the B side (meaning they're self-centered). However, they can build a stable relationship, if the person is an A-ish AB.

O × O: Though their honest attitudes can build a frank and open relationship, they tend to collide with each other when it comes to competition.

O × B: Type O is patient and they can enjoy and support Type B's free wheeling personality. A good pairing!

O × AB: Type O are straightforward and honest, so they may have a hard time understanding AB's complexity at first. But, Type O is resilient and can be supportive, especially when Type AB is facing adversity.

B × B: This can be the best combination when their preferences and pace fit one another. But if they don't, this pairing could be the worst.

B × AB: Type B likes to take time to do things and Type AB values privacy. These two naturally respect each other's wishes. They'll have a good relationship as long as they don't get in each other's way.

AB × AB: Type AB is pretty rare, so two ABs find a strong connection and affection for each other. They can understand the other's complex and unique personality more than anyone else, so the relationship can get intense.

Marriage Success by Blood Type

Blood type relationship pairings don't have to be romantic. But when they are, boy oh boy, watch out! A marriage consultancy agency in Tokyo called Celebrity gathered statistics of successful blood type marriages based on their database of professional matches. They reveal the matches that are the most likely to result in marriage:

O Male × A Female A Male × A Female O Male × B Female O Male × O Female

Do you know any couples who fit these pairs? If so, you might get a wedding invite pretty soon. For more details, check out their page about personalities and tendencies for each blood type.

Blood Type Personality Theory as a Cultural Movement

There's a whole heap of books, movies, dating services, resources, and chocolate that revolve around this obsession with blood types.

As a modern nation rooted in science and technology, you might expect old-fashioned, non-scientific beliefs about blood types to get left behind in Japan. Well, you'd be wrong. Japanese people, especially women, talk about blood type personality theory quite a bit in their daily lives, and it's one of the most common topics at goukon , nomikai , and other social gatherings. Some people are so fanatical that they won't date anyone they're incompatible with blood-wise.

And that's just scratching the surface. There's a whole heap of books, movies, dating services, resources, and chocolate that revolve around this obsession with blood types.

Blood Type Books

Many people love to read, so naturally there are a lot of blood-type-related books. One of the most popular is the Your Blood Type Manual Series 血液型 （ けつえきがた ） 自分 （ じぶん ） の 説明書 （ せつめいしょ ） シリーズ , which calls itself, "instruction manuals for yourself based on your blood type." These books introduce a bunch of physiological and behavioral characteristics of blood types explained with a hand drawn art style. The series was a huge success, and total sales of the series reached nearly 620 million copies. It's so popular that there are even accompanying mobile apps and DVDs.

But why stop at relationships? Why not let your blood dictate your meals, too? Blood Type Diet: Blood Types Have They're Own Diet 血液型 （ けつえきがた ） ダイエット: 血液型 （ けつえきがた ） によって 合う （ あ ） ・ 合わない （ あ ） 食べ物 （ た もの ） がある! is a series of books that recommends specific meal plans based on your blood type. The author, Fumiyasu Nakashima, is a chiropractor and author of many health-related books and articles. His blood type diet theory stretches back through history and ties each blood type to specific groups of prehistoric people. For example, blood type A is linked with agricultural people, so their ideal diet is mainly vegetables and rice.

Blood Type Movies

There are also blood-type-themed movies, shows, and anime. Blood types help to emphasize the characters' personalities. Plus there's a lot of romance tied in with blood types, so that works perfectly in stories.

How Women Get Married Based on Their Blood Type 血液型 （ けつえきがた ） 別 （ べつ ） オンナが 結婚 （ けっこん ） する 方法 （ ほうほう ） ♪ is a special romance series of four episodes featuring four women with different blood types — one for each type. It was broadcasted from Feb 23 - 26, 2009 on Fuji TV.

Ketsuekigata Kun 血液型 （ けつえきがた ） くん！ is a short anime based on a comic written by "Real Crazy Man." The story follows eight characters, male and female for each blood type, all voiced by actors with the corresponding gender and blood type. Every episode features a certain topic, like love, careers, or day-to-day life, showing the different ways each blood type reacts to specific situations.

Blood Type Dating Services

Many Japanese dating sites encourage you to show your blood type on your profile, so it makes perfect sense that there would be dating services that revolve specifically around that concept.

Exciting! Blood Type Goukon わくわく 血液型 （ けつえきがた ） 合コン （ ごう ） is a dating party service that groups men and women based on their blood. The site has a lot of testimonials from satisfied participants who were successfully matched with partners based on blood.

Blood Type Personality Assessment: Atarimasse 血液型 （ けつえきがた ） 性格判断 （ せいかくはんだん ） アタリマッセ is a website that explains each blood type and gives love advice based on the blood of you and your partner. If you're having relationship trouble, go get a blood test and then check out this site.

Other Blood Type Products

It doesn't stop there. There are tons of different blood type products in Japan.

ABOBA is a series of blood type condoms. You pick the condom based on your partner's blood type, which helps… you know, blood. This product also includes brief relationship advice based on your blood pairing.

Japanese toy brand, BANDAI, makes blood type chocolate 血液型 （ けつえきがた ） 別 （ べつ ） オモイアタルくんチョコ！, which comes with a little mascot representing a specific blood type. The package is covered in humorous words that make jokes about blood type personalities. There are 10 variations for each blood type.

akiba:F 献血 （ けんけつ ） ルーム is the coolest (i.e. nerdiest) blood donation center, located in Akihabara. Non-Japanese people can donate blood too, but the service is only offered in Japanese and there are some restrictions for foreigners, so be advised. You'll get to know your blood type, while experiencing the Akiba subculture. There's also free wi-fi, manga, magazines, snacks, and drinks to enjoy while you wait. Get your nerd blood tested, you nerd.

History of the Blood Type Personality Theory in Japan

So where did this blood type obsession come from? And why does it have such a strong hold in Japan? The answer: someone made some casual observations.

In 1927, Psychologist Takeji Furukawa was a teacher at a girls' school attached to a university. He began to question the school's entrance exam system, which was based solely on academic ability. He wanted a system that also considered the applicants' personalities.

Based on this idea, he observed 11 people in his family and noted their blood types. There weren't any AB types in his family, so he lumped them together with A. And voila! From this incredibly tiny focus group, he wrote his famous thesis titled, "The Study of Temperament Through Blood Type." Even though Furukawa's theories were denied by academics in 1933, the theory was too popular to shoot down completely.

After WWII, discussions about the blood typing theory died down for some time. But in the 1970s, a journalist by the name of Masahiko Nomi, who was influenced by Takeji Furukawa, published a book about the relationships between blood types and personalities. This book became a bestseller and helped spread the theory more widely. By the 1980s, the topic was popping up in media like music, TV shows, and magazines. Furukawa's blood type theory had finally hit the big time!

Furukawa observed 11 people in his family and noted their blood types. There weren't any AB types in his family, so he lumped them together with A.

The trend slowed to a crawl in the 2000s because of anti-blood type movements (more on that later). So even though people's personal thoughts about blood type personalities are still fairly strong, there's not as much media about it as there used to be.

It's clear that this series of events created a lot (a lot!) of fanatical believers in the blood type theory in Japan. But, as I've mentioned, there is no scientific evidence to support any of it. So, why do people still believe in this stuff? From a psychological standpoint, this blood type theory has always been a controversial topic. There have been attempts to figure out the statistical relationship between blood types and personalities, but so far nothing's been proven. There has been a lot of research on the social phenomenon itself, with much of it concluding that confirmation bias is the main reason behind people's beliefs.

It's clear that these blood type theories are not real or based on any science. However, there are times I personally still feel like they are true, especially when I meet people whose personalities fit their blood types so well. But that is most likely just my confirmation bias taking over.

Burahara: The Social Problem of "Blood Harassment"

The blood type theory isn't all romance and fun times. It also caused a huge social problem known as burahara ブラハラ, short for "blood harassment." The blood type chart from earlier looks well-balanced, right? Each type has its own set of strengths and weaknesses. But in the real world some features get a lot of attention while others are totally ignored.

Actually, I've experienced and witnessed burahara in my life quite a bit. My blood type is B, the most disadvantaged type in Japan. B types are considered to be selfish and uncooperative. We're also thought of as creative and passionate, but generally, those good traits are overshadowed by the more negative ones. When I tell people I'm B, they ignore the good traits and start making fun of me, saying things like:

あーそうだよね！わかるわかる！めっちゃBっぽいもん。

Oh, I knew it! I can tell you're B, because you're so B-ish.

The implication here is, "Oh, of course you're B! You're selfish and uncooperative, now that I think about it."

It's believed that this discrimination comes from the population ratio.

A = 40%

O = 30%

B = 20%

AB = 10%

One of the biggest advocates of Japan's blood type personality theory is TV shows. So in recent years, these shows have been receiving more and more complaints.

B is in the minority and, as is the case in a lot of situations, people in the minority are put at a disadvantage. Though there are fewer AB than B, in my personal experience, B types are bullied more often than AB, because AB is so rare (at only 10%). People haven't run into enough AB types to know if they really fit the stereotype.

The second most common blood type (O) gets harassed, as well. I've often heard people asking if someone is O, when they do something forceful or rough, like tear open a bag of candy. I've rarely seen situations where A, the most common blood type in Japan, gets picked on for things, but it does happen. For example, if you say things like, "You're not very A-like," it can be interpreted as, "You're not organized enough to be A," putting them down for not meeting the positive expectations placed on them.

Anti-Blood Type Bullying Movements

It's not all blood type bullying though. Minority blood types (like B) are starting to push back.

One of the biggest advocates of Japan's blood type personality theory is TV shows. So in recent years, these shows have been receiving more and more complaints. In 2004, the Broadcasting Ethics & Program Improvement Organization sent requests to television shows, asking that they stop encouraging people to believe personalities are influenced by blood types.. This helped reduce broadcasts about blood type theories quite a bit. And this is why there are fewer programs talking about blood types than there were 10 years ago.

Unfortunately, burahara can be an issue in your career, too. Blood types have been used as criteria for job recruitment and school entrance exams. Though companies have been warned by the government to omit questions about blood types in job applications, the problem might still affect you, if your would-be boss is a big believer in blood stereotyping. If you get a chance to interview for a Japanese company or have a Japanese boss, remember you don't have to answer those questions. You can just say that you don't know your blood type.

Japanese Blood Type Personality Theory and You

Whether or not you believe blood types affect personalities, you can still have fun with this part of Japanese culture. But don't go testing your blood just because you're about to take a trip to Japan. Try to participate when people bring up your blood type (but don't become an offensive burahara bully). And try to read the situation if you're teased about your blood type. Japanese people tend to pick on others as a sign of affection, so if they tease you about your blood type, it probably means that they want to get to know you. Think of the Japanese blood type personality theory as a fun way to strike up a conversation and make new Japanese friends (and nothing more).