Posted on: January 31, 2017 at 10:23 am
Last updated: June 1, 2018 at 3:56 pm

Knowing blood types is an important step in health awareness, especially in a crisis situation. Some people also believe that their blood type tells a certain amount about personality, and in Japan, it’s as frequently asked as your astrological sign(1)!


But can you really tell someone’s personality or optimal diet from their blood type alone?

Here’s a great video with some interesting facts and read on to get the whole list!


What are the blood types?

Human blood is grouped into four major groups A, B, AB, and O. Each letter refers to a kind of antigen, or protein, on the surface of red blood cells. As well, each blood type is also grouped by its Rhesus factor which is the (+/-) sign you see each group often combined with. Blood is either Rh (+) or Rh (-).

These details around blood types become especially important when a blood transfusion is necessary. In a transfusion, a patient must receive a blood type that is compatible with his or her own blood type. If you do not get the right kind of blood during a transfusion, it could result in your body rejecting that transfusion which can be fatal.

1. What are the most common blood types?

Roughly 37% of Caucasians are O (+) making it the most common blood type. Individuals with O (+) blood are capable of donating to people with O (+), A (+), B (+), and AB (+). According to the Red Cross Association, not all ethnic groups have the same mix of these blood types.


Hispanic people, for example, have a relatively high number of O’s, while Asian people have a relatively high number of B’s. The second most common blood type in Caucasians is A (+) with 34%. People with this blood type can donate to people with A (+), and AB (+). The rarest blood type in Caucasians is AB (-) with 1%, and they can donate to people with AB (+), or AB (-) blood (2).

2. The universal donor: Type O (-)

O (-) is known as the universal donor because it can be transfused to almost any patient in need. This makes this blood type particularly important in emergency situations. It is also the safest for newborn infants, especially if they have an underdeveloped immune system. However, this blood type is pretty rare. It is found in one in fifteen individuals, but it’s not uniformly found in all ethnic groups.

It’s found in (2):

  • 8% of Caucasians
  • 4% of African-Americans
  • 4% of Hispanics
  • 1% of Asians

3. O (-) can only accept O (-)


Unfortunately, people with O (-) blood can only receive O (-) blood during transfusions. The individual does not have the three antigens present in other blood types (A, B, and Rh), and due to this O (-) blood will only accept other O (-) blood. Any other blood group will lead to an immune attack against the foreign antigen (2).

 4. The second rarest blood type: A (-)


A (-), being the second rarest blood type, makes maintaining a proper supply of this blood in blood banks and hospitals very important. It is present in only about one in sixteen individuals. This means only six point six percent of the population has A (-) blood. But it is also not uniformly found across all races.

It’s found in:

  • 7% of Caucasians
  • 2% of African Americans
  • 2% of Hispanics
  • 0.5% of Asians (2).

5. Only a few can donate to help an A (-)

As a result of having antigen A but no Rh antigen in the blood, A negative can only receive blood type A (-) and O (-). Any other blood group would trigger an immune response. The flip side is that A (-) can be given to other people with A (-), A (+), AB (-) and AB (+) (3).

6. A (+) is the second most common blood type

People who have A positive, have the second most common type of blood, it’s present in one out of three individuals. However, as with other blood types, it’s not present uniformly across all races.

It’s found in:

  • 33% of Caucasians
  • 24% of African Americans
  • 29% of Hispanics
  • 27% of Asians

Not everybody knows their blood type but you definitely should, because one day you could be called on to save someone’s life. In an emergency, you might need blood, or you could be susceptible to certain conditions that you should be aware of. If you happen to have a universal donor type or a very rare type of blood, people might need you to donate.

7. Is the blood type diet real?

The short answer to this is no. Although there was some preliminary research done back in the 1950’s on the different blood types and diet, that theory has largely been disproven.  In a 2014 study performed by Wang et al. on 1455 people they found that although following certain ‘Blood-Type’ diets were associated with some positive effects on cardiovascular and metabolic risk factors, these associations had nothing to do with an individual’s ABO genotype, so the findings do not support the ‘Blood-Type’ diet hypothesis (4).

8. Do different blood types have different personalities?

In Japan, there is a strong belief that a person’s blood type is predictive of a person’s personality, temperament, and their compatibility with others — similar to asking someone their astrological sign. Type A’s, they believe, are perfectionists and make good accountants; Type B’s are sociable but selfish; O’s are said to be decisive and curious, while AB’s are supposedly complex and suited for research and art (5).

So is there any truth to the theory? Skeptics are quick to point out that blood type is determined by the proteins in the blood – which is hardly a predictor of someone’s character. “It’s mere superstition,” says Tatsuya Sato, associate professor of psychology at Ritsumeikan University. “Linking blood type and personality is not only unscientific, it’s wrong.” Several studies have also been put forth to disprove the theory (6). Nevertheless, it is interesting to know about!

9. Different kinds of animals have different kinds of blood

Did you know that dogs are similar to humans and have 4 blood types, cats have 11, and cows have almost 800?

10. Every two seconds someone in the U.S. needs blood

If you currently donate blood (well done!) in a single session they usually collect roughly about 450 ml (a pint) of blood during a single blood donation. To give you an example of how much blood is needed in an emergency situation, the average red blood cell transfusion is approximately 3 pints where as a single car accident victim can require as many as 100 pints of blood (2).

Furthermore, according to Red Cross:

  • Approximately 36,000 units of red blood cells are needed every day in the U.S.
  • Nearly 7,000 units of platelets and 10,000 units of plasma are needed daily in the U.S.
  • Nearly 21 million blood components are transfused each year in the U.S.

To keep up with the demand almost 41,000 daily donations are needed… which means that every donation helps.  If you haven’t donated yet, now’s your chance to get out and donate!


(1) Fact Monster. Blood types Accessed: January 25, 2017.

(2) Red Cross. Blood Types. Accessed: January 25, 2017.

(3) Thrombocyte. 10 A negative blood type facts Accessed: January 25, 2017.

(4) Wang J, García-Bailo B, Nielsen DE, El-Sohemy A (2014) ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors. PLoS ONE 9(1): .

(5) Yamaguchi, Mari (6 May 2005). “Myth about Japan blood types under attack”. MediResource Inc. Archived from the original on 28 December 2009. Retrieved January 25, 2017.

(6) Scientific American. You are what you bleed: In Japan and other east Asian countries some believe blood type dictates personality. Published February 15, 2011.  Retrieved January 30, 2017

(7) Youtube. 10 little-known facts about blood Published: March 7, 2014. Accessed: January 25, 2017.

Dr. Nadia Kumentas ND
Co-founder at Affect Health
Nadia Kumentas is a Toronto-based naturopathic doctor, tea drinker, yoga doer, animal lover, and plant enthusiast. She is also the co-founder of Affect Health, a professionally formulated medicinal tea company. "

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