People across East, Southeast, and South Asia carry a blood-type profile that differs from European and African populations in several measurable ways. The differences go well beyond the familiar A-B-O split. Asian populations have a distinctly higher frequency of blood type B, an extremely low rate of Rh-negative blood, and a set of rare blood-group variants that are either unique to or far more common in people of Asian descent. These patterns have real consequences for transfusion medicine, pregnancy management, organ transplantation, and even infectious disease risk.
How ABO Types Are Distributed in Asian Populations
In China, the largest studied Asian population, the overall ABO ranking runs O, A, B, AB, with the O gene frequency at about 0.58, followed by A at 0.21 and B at 0.21, making A and B almost equally common.1PubMed Central. Distribution characteristics of ABO blood groups in China That near-equal split between A and B is striking because in most European populations, type A vastly outnumbers type B. The relatively high frequency of B is one of the most consistent features of Asian blood-type data, and it shows up across East, Central, and South Asia.
Within China alone, the variation between ethnic groups is substantial. Among Yi people, type A reaches about 34%. The Manchu and Mongolian groups have some of the highest B frequencies, around 33%. The Zhuang group in southern China has an especially high proportion of type O at roughly 42%, while AB is most common in the Uyghur population at about 11%.2PubMed Central. Frequencies and ethnic distribution of ABO and RhD blood groups in China: a population-based cross-sectional study These internal differences remind us that “Asian” is not a single genetic population. When researchers talk about Asian blood-type patterns, they are describing broad tendencies that can shift considerably by region and ethnic background.
One evolutionary explanation for the elevated B frequency in parts of Asia involves cholera. Research has shown that people with type O blood face greater susceptibility to severe cholera, and the sustained selective pressure of cholera epidemics over centuries in regions like the Gangetic Delta may have pushed O gene frequencies down while B frequencies rose.3PubMed. Predisposition for cholera of individuals with O blood group. Possible evolutionary significance This is one of the clearest examples of how infectious disease can sculpt the blood-type landscape of an entire region.
Why Rh-Negative Blood Is Extremely Rare
In European-descended populations, around 15% of people are Rh-negative (commonly written as “Rh−” or “D-negative”). In most East and Southeast Asian populations, that number drops to 0.5% or less.4PubMed Central. DEL in China: the D antigen among serologic RhD-negative individuals The practical impact is enormous. Rh-negative blood units are chronically scarce in Asian blood banks, which creates challenges for transfusion and for managing Rh-incompatible pregnancies.
Among China’s 56 recognized ethnic groups, most share this very low Rh-negative rate. The Uyghur population is a notable exception, with an Rh-negative frequency reaching about 4.7%, likely reflecting genetic admixture with Central Asian and European populations.4PubMed Central. DEL in China: the D antigen among serologic RhD-negative individuals Even so, 4.7% is still well below the roughly 14% seen in the United States.
The rarity of Rh-negative blood in East and Southeast Asia has pushed clinicians to investigate workarounds. One of the most promising involves a variant called “DEL,” discussed in the next section, which could ease the demand for scarce Rh-negative red cells and Rh immune globulin (RhIG) in the region.5Blood Global Hematology. Asian-type DEL among D-negative patients and donors in Malaysia can ease the demand for D-negative red cells and RhIG
The DEL Phenotype and What It Means for Transfusions
Among people in East Asia who test as Rh-negative using standard methods, a surprisingly large fraction, roughly 17%, actually carry an extremely small amount of the D antigen on their red blood cells. This is the DEL phenotype, named because the D antigen can only be detected by a sensitive absorption-elution technique. The most common form in Asia, called Asian-type DEL, is caused by a specific genetic variant (RHD*DEL1).5Blood Global Hematology. Asian-type DEL among D-negative patients and donors in Malaysia can ease the demand for D-negative red cells and RhIG
Why does this matter? A recent prospective clinical trial found that patients with Asian-type DEL can be safely managed as if they are D-positive. Their red blood cells produce only a tiny trace of full-length RhD protein, roughly 0.18% of total transcripts, but this appears to be enough to create immune tolerance against D-positive blood.6PubMed Central. Asian-type DEL red blood cell transfusion and pregnancy outcomes In practical terms, correctly identifying DEL donors could stretch the limited supply of Rh-negative blood by reclassifying many of those donors as safe for D-positive transfusion, and spare pregnant DEL women from unnecessary RhIG injections.
The molecular basis is well characterized. In DEL individuals carrying the RHD 1227A allele, the gene produces several abnormal mRNA transcripts. Normal full-length RhD mRNA is absent because a mutation at the end of exon 9 causes that exon to be consistently spliced out, meaning no normal RhD protein is made.7PubMed. Multiple isoforms excluding normal RhD mRNA detected in Rh blood group Del phenotype with RHD 1227A allele The result is a phenotype that looks negative on routine testing but is biologically closer to a very weak positive.
The Diego Blood Group System
Outside the familiar ABO and Rh systems, one of the most distinctive blood group markers in Asian populations is the Diego antigen, specifically the Di(a) variant. This antigen is virtually absent in people of European and African descent but is found in roughly 3–5% of individuals in mainland China and about 9–10% of people in Japan and Mongolia.8Scientific Reports. Detection of the distribution frequency of Diego blood type based on multiplex droplet digital PCR9PubMed. Prevalence of diego blood group Dia antigen in Mongolians: comparison with that in Japanese In a Malaysian study, the Di(a) antigen was found in about 4% of ethnic Chinese donors, 1.25% of Malays, and under 1% of Indian donors.10PubMed Central. Prevalence of Diego blood group antigen and the antibody in three ethnic population groups in Klang valley of Malaysia
Diego has been remarkably useful as an anthropological tracer. Because it is common in East Asian populations and present at extremely high frequencies (40–54%) in Indigenous peoples of the Americas, it has long been used to track the ancient migration of Northeast Asian populations across the Bering Strait.8Scientific Reports. Detection of the distribution frequency of Diego blood type based on multiplex droplet digital PCR A genetic study tracing the DI*01 allele found that its highest frequencies appear in Mongolia, Turkmenistan, and Kyrgyzstan, with a radial expansion pattern that closely tracks the movements of Altaic-speaking nomadic groups over the past two millennia.11PubMed Central. The radial expansion of the Diego blood group system polymorphisms in Asia: mark of co-migration with the Mongol conquests
Miltenberger Antigens in Taiwan and Southeast Asia
In Taiwan, blood banks have a concern that most of the world does not share. The Miltenberger subtype III antigen, known as Mi.III or GP.Mur, is so common there that it is considered the second most important blood group antigen after ABO. The GP.Mur phenotype occurs in about 7.3% of Taiwan’s general population and reaches strikingly high rates in some indigenous Taiwanese groups, between about 21% and 88%.12PubMed Central. Miltenberger blood group antigen type III (Mi.III) enhances the expression of band 313PubMed. Selection of GP. Mur antigen-negative RBC for blood recipients with anti-‘Mi(a)’ records decreases transfusion reaction rates in Taiwan
The antigen is a hybrid of two glycophorin proteins on the red cell surface. Because it is so prevalent, about 1.24% of people in Taiwan develop antibodies against it. Taiwanese blood banks routinely screen for these antibodies, and selecting GP.Mur-negative blood for patients who have developed anti-Mia antibodies has been shown to reduce transfusion reaction rates.13PubMed. Selection of GP. Mur antigen-negative RBC for blood recipients with anti-‘Mi(a)’ records decreases transfusion reaction rates in Taiwan This is a blood-banking challenge that is essentially invisible outside of East and Southeast Asia.
Interestingly, the GP.Mur phenotype appears to have a physiological upside. Red cells carrying it express 25–67% more band 3 protein, a chloride/bicarbonate exchanger, on their membranes. This gives them a larger capacity for the gas exchange reactions involved in CO₂ transport.14ISBT Science Series. Physiological Implications of Miltenberger blood group antigen subtype III (Mi.III) Whether this translates to any measurable advantage in aerobic capacity or altitude tolerance remains an open question, but it is a tantalizing possibility given the high prevalence in some mountain-dwelling indigenous populations.
Cis-AB, a Variant That Confuses Standard Typing
Most people inherit one ABO allele from each parent. In rare cases, a single allele encodes an enzyme that can produce both A and B antigens. This variant is called cis-AB, and while it exists worldwide, it is the most frequent ABO subgroup in Korea and occurs more often in East Asia than anywhere else.15PubMed Central. Cis-AB, the Blood Group of Many Faces, Is a Conundrum to the Novice Eye
Cis-AB can produce apparently paradoxical family inheritance patterns. For example, an AB mother could give birth to a type O child, a result that seems impossible under standard ABO genetics and has historically raised false suspicions about paternity. The explanation is that both A and B antigens came from a single parental allele rather than one from each parent.16PubMed. The cis-AB blood group phenotype: fundamental lessons in glycobiology When cis-AB is paired with a normal A or B allele on the other chromosome, it can also produce phenotypes that look slightly off on routine testing, leading to misclassification. That misclassification is not just a labeling problem. If a cis-AB individual receives blood typed under the wrong assumption, it can trigger a hemolytic transfusion reaction.15PubMed Central. Cis-AB, the Blood Group of Many Faces, Is a Conundrum to the Novice Eye
The Duffy System and Malaria Resistance
The Duffy antigen receptor on red blood cells serves as an entry point for the malaria parasite Plasmodium vivax. In sub-Saharan African populations, a Duffy-negative phenotype is extremely common and provides near-complete resistance to vivax malaria. In most Asian populations, however, the predominant phenotype is Fy(a+b−), meaning the cells carry the Fy(a) form of the antigen. This phenotype does not block the parasite entirely, but it does reduce binding of the parasite’s key invasion protein by 41–50% compared with the Fy(b) form.17PubMed Central. Fy(a)/Fy(b) antigen polymorphism in human erythrocyte Duffy antigen affects susceptibility to Plasmodium vivax malaria
A prospective study in the Brazilian Amazon found that people with the Fy(a+b−) phenotype had a 30–80% reduced risk of clinical vivax malaria, though the protection did not extend to falciparum malaria.17PubMed Central. Fy(a)/Fy(b) antigen polymorphism in human erythrocyte Duffy antigen affects susceptibility to Plasmodium vivax malaria Because vivax malaria has been historically endemic across much of Southeast Asia, some researchers believe the high prevalence of the Fy(a) allele in Asian populations reflects long-term natural selection favoring partial resistance.18PubMed. Duffy antigen receptor for chemokines (DARC) and susceptibility to Plasmodium vivax malaria
Blood Type and Disease Risk
Beyond malaria, ABO blood type has been linked to several chronic diseases, and some of the strongest data come from large Asian cohorts. For gastric cancer, type A consistently shows an elevated risk. A case-control study and meta-analysis found that people with type A had roughly a 10–15% higher risk of gastric cancer than non-A individuals, while type O appeared mildly protective.19PubMed Central. ABO Blood Group System and Gastric Cancer: A Case-Control Study and Meta-Analysis A large Taiwanese cohort of over 339,000 people confirmed the pattern, finding that type A was associated with about a 38% higher risk of stomach cancer incidence compared with type O.20PubMed Central. ABO blood types and cancer risk–a cohort study of 339,432 subjects in Taiwan
The connection between ABO type and blood clots is also well documented. A study of Chinese Han patients found that people with non-O blood types had about 2.5 times the odds of deep vein thrombosis compared with type O individuals, with the AB group facing the highest risk at more than four times the odds.21PubMed Central. ABO blood groups and risk of deep venous thromboembolism in Chinese Han population from Chaoshan region in South China A much larger hospital-based study of 200,000 Chinese patients confirmed the overall trend, finding that any non-O blood type carried about a 36% higher odds of venous thromboembolism.22Scientific Reports. ABO blood types associated with the risk of venous thromboembolism in Han Chinese people: A hospital-based study of 200,000 patients These associations are not unique to Asian populations, but they are relevant because the high combined frequency of B and AB types in Asia means a larger share of the population falls into the higher-risk non-O category.
During the COVID-19 pandemic, several studies examined whether blood type influenced infection risk. A systematic review and meta-analysis found that type A and type B individuals had modestly higher odds of contracting COVID-19, while type O appeared somewhat protective.23PubMed Central. The impact of ABO blood group on COVID-19 infection risk and mortality: A systematic review and meta-analysis However, at least one cohort study found that after adjusting for age, sex, and existing health conditions, no blood group was significantly linked to disease severity or death.24PLOS ONE. Association of ABO blood group with COVID-19 severity, acute phase reactants and mortality The upshot is that any blood-type influence on COVID outcomes was likely small and may have been confounded by other factors.
Transfusion Challenges Across Populations
When the blood supply comes predominantly from donors of one ethnic background and the patients come from another, antigen mismatches pile up. A study of transfusion-dependent thalassemia patients of predominantly Asian descent found that differences in the K, c, S, and Fy(b) antigens between white donors and Asian patients accounted for 38% of the alloantibodies the patients developed.25Blood. Alloimmunization and erythrocyte autoimmunization in transfusion-dependent thalassemia patients of predominantly Asian descent Each new antibody narrows the pool of compatible blood even further and increases the risk of future transfusion reactions. For patients who need blood regularly, like those with thalassemia or sickle cell disease, this is a serious and compounding problem.
ABO incompatibility also matters in pregnancy. ABO hemolytic disease of the fetus and newborn can occur when, for instance, a type O mother carries a type A baby. While usually milder than Rh disease, severe cases do happen. A case series documented three neonates, all type A born to type O mothers, who required blood exchange transfusions due to dangerously high bilirubin levels driven by maternal anti-A antibodies.26PubMed Central. Severe ABO hemolytic disease of fetus and newborn requiring blood exchange transfusion These cases are a reminder that even the most common blood-group system can cause serious clinical problems.
Rare blood registries have become an important solution. An Indian initiative demonstrated that implementing a regional rare donor registry significantly reduced the time needed to locate compatible blood for patients with unusual phenotypes.27PubMed Central. Implementation of a regional rare donor registry in India Similar registries exist in several Asian countries, and expanding them remains a priority for transfusion services dealing with the region’s uniquely distributed antigen landscape.
ABO-Incompatible Organ Transplantation
The scarcity of matching donors in some Asian blood-type pools has driven innovation in transplant medicine. ABO-incompatible kidney transplantation, once considered too risky, was pioneered with improved outcomes by Japanese transplant centers in the early 2000s. The approach involves removing ABO antibodies before surgery and maintaining aggressive immunosuppression afterward, and current results are comparable to those of ABO-compatible transplants.28PubMed Central. Current progress in ABO-incompatible kidney transplantation In Singapore, ABO-incompatible living kidney donor transplants have continued through the COVID-19 era with low-dose desensitization protocols.29Proceedings of Singapore Healthcare. A retrospective cohort study of ABO incompatible living kidney donor transplantation before and during the COVID-19 pandemic This work has been directly accelerated by the reality that in Asian populations, where the B type is very common and Rh-negative donors vanishingly rare, waiting for a perfectly matched donor can mean waiting indefinitely.
The Bombay Phenotype and Its Risks
One of the rarest and most dangerous blood-typing surprises involves the Bombay phenotype, first identified in Mumbai. Individuals with this phenotype lack the H antigen, the precursor molecule on which both A and B antigens are built. Their red cells test as type O on routine typing, but they carry potent anti-H antibodies that make ordinary type O blood incompatible. Transfusion with standard O blood can cause a life-threatening hemolytic reaction.30PubMed Central. Navigating transfusion challenges: Bombay blood group in focus
The Bombay phenotype occurs at very low frequencies worldwide but is more commonly reported in India and parts of Southeast Asia than in European populations. A case report described a 49-year-old woman who was transfused standard type O blood at a peripheral hospital and suffered a hemolytic transfusion reaction because her Bombay phenotype had not been identified.30PubMed Central. Navigating transfusion challenges: Bombay blood group in focus The only safe transfusion option for Bombay individuals is blood from other Bombay donors, making rare blood registries a matter of life and death for these patients.
Blood Type Personality Beliefs in Japan and Korea
No discussion of blood types in Asia would be complete without addressing the cultural phenomenon of blood-type personality theory. Widely popular in Japan and South Korea, the idea holds that ABO blood type determines temperament: type A people are supposedly careful and anxious, type B are creative and selfish, type O are confident and insensitive, and so on. Books on the topic regularly become bestsellers, and blood type is a common topic in casual conversation and even dating.
One large study of healthy Japanese subjects did find a statistically significant association between ABO genotypes and one personality trait, but the researchers themselves cautioned that the association was weak and should be treated as preliminary.31PubMed Central. ABO Blood Type and Personality Traits in Healthy Japanese Subjects The broader scientific consensus is that blood type has no meaningful predictive power for personality. The persistence of the belief speaks more to cultural momentum than to biology. It is worth being aware of, though, because the popularity of blood-type thinking in parts of Asia can sometimes create real social consequences, including workplace discrimination and relationship stigma directed at people with type B blood.
Forensic DNA Phenotyping and Population-Specific Markers
Advances in forensic genetics have begun incorporating population-specific traits that are relevant in Asian contexts. Forensic DNA phenotyping, the prediction of visible physical traits from DNA left at a crime scene, has expanded beyond eye and hair color. A prediction model developed for northern Chinese populations achieved strong accuracy for predicting both alcohol flush reaction and body odor phenotype based on 19 genetic variants.32Forensic Sciences Research. Forensic DNA phenotyping: construction and evaluation of a 19SNPs phenotype prediction system based on the Chinese population Separate work on Thai populations has focused on skin color prediction, examining genes involved in melanin production that vary in frequency across Asian groups.33PubMed Central. Prediction of Skin Color Using Forensic DNA Phenotyping in Asian Populations: A Focus on Thailand These developments illustrate how genetic variation among Asian populations is being characterized with increasing precision, though they also raise ethical questions about the use of ancestry-linked genetic data in law enforcement.