Dr. Karl Landsteiner won the Nobel prize in 1930 for developing the ABO blood group system. The ABO system is the best known method of classifying blood types.

It’s important to know your blood type if you need to receive or give blood. But some research suggests knowing your blood type could also alert you to certain types of autoimmune diseases you may be more likely to develop such as Hashimoto’s disease or rheumatoid arthritis.

Keep reading as we take a deeper look at the connection between blood types and autoimmune diseases.

Your blood type is determined by a type of protein found on your red blood cells called antigens. Depending on the type of antigens you have, your blood type is classified as:

  • Type A: blood containing A antigens
  • Type B: blood containing B antigens
  • Type AB: blood containing A and B antigens
  • Type O: blood containing neither A nor B antigens

You’ve likely also heard of blood types referred to as “positive” or “negative.” This part of your blood type is determined based on the presence of another antigen called Rh factor.

People with a positive blood type (Rh+) have the antigen on the surface of their red blood cells, and people with a negative blood type (Rh-) do not.

An autoimmune disease is a condition that develops when your immune system attacks healthy cells in your body. It’s still not clear why some people develop autoimmune diseases, but it’s thought that genetics and environmental factors can both play a role.

Some autoimmune conditions, such as multiple sclerosis (MS), are more common in people with a family history of the disease. Research has also found that women are almost twice as likely to develop an autoimmune disease as men.

There’s evidence that some autoimmune diseases are more common in people with certain blood types. However, the results of many studies examining this link have been inconsistent, often due to small sample sizes.

In the following sections, we’ll examine the research findings to date on blood types and their connection to specific autoimmune diseases.

Type 1 diabetes is thought to be an autoimmune disease where your body attacks cells in your pancreas.

Type 2 diabetes is when your body becomes resistant to the hormone insulin or doesn’t produce enough insulin. Some researchers hypothesize that type 2 may also be an autoimmune disorder, but more research is needed to understand how it develops.

The data is conflicting in this area, as you can see from some recent research results:

  • A 2020 study found that in a group of 424 people, O blood type was associated with a decreased risk of type 2 diabetes, and blood type B was associated with an increased risk.
  • Another 2020 study looked at 750 participants and found that risk of developing type 2 diabetes was higher in blood group A than those in any other blood group.
  • In a 2017 study from Pakistan, researchers found similar results. They discovered that in a group of 2,258 university students, people with a B blood type were more likely to develop diabetes than those with other blood types.
  • A large 2015 study of 82,104 women showed that people with type O blood had a lower risk for type 2 diabetes, while both A and B blood type groups were shown to be at a higher risk with no association in Rh factor.

Overall, the data regarding blood type and its association with diabetes is still very conflicting and requires continued research.

Rheumatic disease is a group of more than 200 conditions that cause pain in your joints, connective tissue, tendons, and cartilage. Many of these conditions are autoimmune disorders.

A 2017 study from Turkey examined the connection between blood type and the prevalence of autoimmune rheumatic disease. The researchers found that some conditions were more common in people with certain blood types.

Diseases that were most common in people with type A blood were:

Diseases more common in people with type O were:

All diseases were less common in people with blood type AB.

Most people with rheumatic disease — 92.2 percent — had an Rh+ blood type.

Lupus is an autoimmune disease that causes inflammation and pain throughout the body. The symptoms are usually concentrated in one area such as your joints, skin, or organs.

The most common cause of lupus is called systemic lupus erythematosus.

A 2019 study from Iran found that in a group of 146 people with systemic lupus erythematosus, those with blood type A or B had more severe symptoms than people with other blood types.

In a Brazilian study from 2009, researchers found no difference in blood type ratios between people with discoid lupus erythematosus and the local population. However, they did find that blood type A was associated with an increased risk of experiencing symptoms outside the head and neck.

There are two main types of inflammatory bowel disease (IBD)ulcerative colitis and Crohn’s disease.

Here is a brief overview of some of the recent data on IBD and blood type:

  • A 2016 Chinese study found no association between blood type and the prevalence of Crohn’s disease in a group of 293 people. The researchers found that people with blood type AB responded better to the medication infliximab, while those with type A seemed to have an increased risk for losing response to it.
  • A 2020 study found no association between the prevalence of ulcerative colitis and blood type in a group of 129 patients from Taiwan.
  • A 2020 study from Korea showed a possible protective effect of having blood type O in those with Crohn’s disease.
  • A 2014 study involving participants from Italy and Belgium demonstrated similar results of the 2020 Korean study above, showing that those with blood type O had a lower chance for developing Crohn’s disease or having a severe form of the disease.

MS is an autoimmune condition that occurs when your immune system attacks a protective layer around your nerves called myelin.

A 2019 study found that in a group of 265 people, those with blood type A+ or B+ had an elevated risk for developing MS. The study also found that people without the antigens A, B, or Rh+ had a decreased risk.

Researchers haven’t established a link between celiac disease and blood type.

Most people with celiac disease have antibodies in their blood specific to the disease. It was theorized that celiac disease could be transmittable through blood transfusions, but a Swedish study examining more than a million people over a 44-year period found no evidence to support this.

Hashimoto’s disease is the most common cause of underactive thyroid in the United States. It’s caused by your immune system attacking and damaging thyroid cells.

A 2019 study found evidence that there may be an association between having blood type O and Hashimoto’s disease. A group of 958 people with thyroid disease were included in the study, and 550 of these people had Hashimoto’s disease.

The ratio of people with blood type O was found to be higher among those with Hashimoto’s than in people with other thyroid diseases. They also found that autoimmune diseases were reported significantly less often in people with blood type AB.

Alopecia areata is an autoimmune condition that leads to patchy hair loss.

A 2018 study found no link between the development of alopecia areata and any particular ABO blood group. They did find that alopecia areata had a small but statistically significant association with Rh+ blood types.

Pemphigoid is a rare autoimmune disorder that causes rashes and blistering.

A 2016 study found no evidence linking blood type to the likelihood of developing pemphigoid disease.

Here is an at-a-glance look at the autoimmune diseases we’ve discussed and the risk of developing them based on blood type.

ConditionSubtypesBlood types with elevated risk
diabetestype A or B
rheumatic diseasespondyloarthropathy
undifferentiated connective tissue disease
Behçet’s disease
rheumatoid arthritis
type A
rheumatoid diseasefamilial Mediterranean fever
systemic sclerosis
Sjögren’s syndrome
type B
lupusSystemic lupus erythematosus possibly type A or B
IBDCrohn’s disease
Ulcerative colitis
lower risk in type O
MStypes A+ and B+
Hashimoto’s diseasetype O
celiac diseaseno association found
alopecia areataRh+ blood type
pemphigoid diseaseno association found

Researchers still don’t understand why some people develop autoimmune diseases and others don’t. It’s thought that genetics and environmental factors both play a role in the development of many conditions.

Studies suggest that some types of autoimmune diseases, such as Hashimoto’s disease and MS, may be more common in people with certain blood types. More comprehensive studies are needed to fully understand this link.