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Just my type: can blood type affect personality?

Senior Lecturer in Biomedical Science at the University of Sunderland Martin Maley explores the issues and puts a theory to the test.

For most of us, I imagine if we were asked about how much our blood groups control our lives, the answer would probably be “not very much”. But what if it did? What if your ABO blood type meant you were expected to act a certain way and display a certain, specific set of personality characteristics?

What if it meant you were recommended to only to eat certain foods, use certain products, apply for certain jobs, and even date certain people, all based on your blood group? For many in the Far East – and Japan, in particular – ABO blood type is of great importance, and can have a massive bearing on how people live their everyday lives.

Masahiko Nomi

Nomi was born in Kanazawa, Ishikawa in 1925 and graduated from the engineering faculty of University of Tokyo. His first book, Understanding Affinity by Blood Type, became a best seller in 1971. His idea of “blood type = personality type” became firmly embedded in Japanese popular culture (and the cultures of some other East Asian countries). After Nomi’s death in 1981, his son, Toshitaka Nomi continued his work.


The advent of linking blood groups to personality characteristics in particular dates back to the 1920s. However, it did not really embed as part of popular culture until the 1970s when a journalist named Masahiko Nomi began publishing theories related to the subject (see below). Although the people and institutions linked to the theories had no medical or scientific credibility – and there have still been no convincing scientific studies proving a link – it has become so widespread that there is now an Institute of Blood Type Humanics in Japan that oversees the work.


To test the theory, in my previous role at NHS Blood and Transplant, I set out to survey a proportion of the UK (deliberately choosing a body of people where there will have been little or no previous importance placed on blood group) to see if, for example, all group O people are confident, assertive, born leaders, whilst also being over-competitive and stubborn. I wanted to see if all group A individuals are sensitive, law-abiding and punctual. Are all group B people disorganised, impatient and over-emotional? And are all AB subjects aloof, shy and retiring? That is what some theories, books and websites suggest.

It doesn’t just stop at personality characteristics. There is the blood group diet, blood group workouts and blood group dating agencies, all of which are very specific about what is expected of you linked to your ABO blood group.

Over 90% of the general public in Japan know their blood type (<90% of the UK transfusion population know their blood group and, therefore, >10% were unable to take part in the survey). It is expected that you have it on your CV if you are applying for a job in Japan. Characters in many Japanese video games have for many years had their blood type displayed as part of their profile. Products readily available to purchase that are targeting compartmentalisation by blood group include blood-type perfumes, bath salts, tea, vitamin supplements, and even condoms (2 billion blood-type condoms are sold in Japan every year).

There are several series of books that deal with the subject, many of which have sold millions of copies.

Indeed, some blood-type diet books have been translated into as many as 65 languages. There is, however, a very serious side to all of this, which is felt especially by group B men, who have a reputation for displaying a certain group of less than desirable characteristics.

There is a specific term “burahara” which translates as “blood group harassment” applied to individuals who are harassed or discriminated against primarily because of their blood group. It reached the point, after several blood group-themed films had been released, that the Japanese TV authorities reached out to programme and film makers to try to help stop the propagation of these theories because of these negative aspects (a summary of the theories that are applied to the four ABO blood groups can be seen overleaf).

Put to the test

The survey that we undertook looked at people self-assessing themselves (an immediate limitation of the study) on their personality characteristics. It was sent out mainly within the blood transfusion community and garnered 1500 completely anonymous responses. This ensured that we had sufficient numbers so any significance found would be statistically sound (see Fig 1 for a breakdown of respondent blood type).

Blood-group products include perfumes, bath salts, tea, vitamins and even condoms

The indices used were based on the characteristics that had been used in previous studies by Swan in the 1980s (no significance found), and Matsui in the 2000s (some significance in AB subjects, but invalidated by low numbers). They included asking people to rate themselves from 1 to 5 on whether they thought they were cheerful, punctual, funny, loyal, artistic, outgoing and confident. We also left a space for survey participants to leave free text comments, some of which were very enlightening. For example:

“I believe there could possibly be a link between blood group and personality. I do, however, believe that this could also be affected by environment and lifestyle.”

“Personality would most likely depend on brain neurones and a few minutes google search didn’t show any ABO blood antigen receptors in neurons.”

“I have twins who have the same blood group as myself and my husband and their little brother, however, all five of us have different personalities.”

“I think more people would believe in blood group personalities if they were talked about more and became part of our culture, as they have in Japan.”

It is also worth mentioning that 362/1500 (24%) of respondents were prepared to believe there may be a link between personality and blood group, and even more – 546/1500 (36%) – were prepared to believe there may be a link with diet. This goes to prove that scientists are open minded, if you can provide them with accompanying evidence.

No statistical evidence

The data we received were analysed using a statistical package including one-way ANOVA (parametric), and Kruskal–Wallis (non-parametric) testing. We found there to be no statistical evidence of a relationship between any individual personality characteristic and any of the four blood groups.

Recently there have also been several scientific publications looking at a possible link between ABO blood type and COVID outcomes (ranging from severity of symptoms, through likelihood of hospitalisation and mortality). There are some that have purported to have found a statistical significance suggesting group O individuals have somewhat greater protection from COVID. However, upon further analysis of these studies, it has been suggested that many not only have a high likelihood of bias in the selection of subjects and treatment of results, but have also not sought to deal with this bias in their publications. Only two papers escaped with a low enough sign of bias to be credible, and those studies did not find any link with any of the outcomes.

We found there to be no statistical evidence of a relationship

Group O

Descended from hunter gatherers (cave dwellers), should have a diet rich in meat, are natural leaders, ambitious, sociable, but arrogant, ruthless and demand to be the centre of attention. Group O individuals, because of their origins, should have a higher percentage of persons with blonde / red hair, blue eyes, and body piercings / markings / tattoos. Workout should be strenuous (running, swimming, cycling).

Group A

Descended from ancient farmers, should have a vegetarian diet rich in beans, whole grains and legumes that should be organic and fresh to aid their sensitive immune system. They are considered reserved, restrained, and cool when angry, but over-sensitive and fussy. Workout should be slower and less intense (tai chi and pilates).

Group B

Descended from nomads, should have a diet rich in green vegetables, eggs, and low-fat dairy, whilst avoiding certain other foods, such as wheat, corn, and lentils. They are unpredictable, passionate, confident, yet impulsive, impatient and don’t like taking orders. Workout should include aerobics, swimming, and hiking.

Group AB

Inherit characteristics from A and B groups. Should consume tofu, seafood, and dairy. Characteristics include being understanding, organised, rational and cool, whilst also being indecisive and retiring. Workout should include low-intensity pursuits, such as tennis and yoga.


In summary, there have been many attempts to link ABO types of individuals to a hugely diverse number of “outcomes”. Some have been successful and are supported by data – group O individuals are at higher risk of peptic ulceration and Fy(a-, b-) individuals are provided with a higher level of protection from malaria. However, there are as yet no credible scientific studies that can statistically link ABO type to personality traits.

Perhaps the most telling way to look at the association would be to go right back to the man who first distinguished the main blood groups in 1901 – Karl Landsteiner, who was group O. However, we also know that he was a profoundly serious and solitary man – traditionally traits of group AB individuals.  

Martin Maley is a Senior Lecturer in Biomedical Science in the Faculty of Health, Science and Wellbeing at the University of Sunderland. He is also NHS Blood and Transplant Honorary OD Consultant and the IBMS Transfusion Deputy Chief Examiner.


Image credit | Getty


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