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What is my blood group?

Have you ever wondered what your blood group actually is? In this article we briefly explain what blood groups there are, why it is useful to know your blood group and how you can find out what it is.

Blood groups

A number of different systems are used to classify blood types. The most common system is the ABO system, often in combination with the so-called rhesus factor.

Find out more about the heredity of blood groups

AB0 system

The AB0 system distinguishes between four main blood groups. These are A, B, O and AB. If you have blood group A, you produce antibodies against blood group B. Antibodies are proteins that humans produce to fight foreign substances that have entered the body. If you have blood group B, you produce antibodies against blood group A. People with blood group O produce antibodies against both A and B, while if your blood group is AB, you do not produce any antibodies against other AB0 blood groups.

Resus factor

The rhesus factor determines whether your blood is ‘rhesus positive’ (+) or ‘rhesus negative’ (-). If you are rhesus positive, your blood contains a specific protein. This protein is not present if you are rhesus negative and is not recognised as one of the body’s own substances. As a result, antibodies can be produced if someone with rhesus-negative blood comes into contact with rhesus-positive blood, even if the blood is from the same AB0 blood group. If a person with rhesus-positive blood is given rhesus-negative blood, no antibodies are produced.

what is my blood group?

Why would you want to know your blood group?

Knowing what your blood group is could be useful for various reasons. Blood transfusions and blood donation are obvious examples. However, it is also a good idea to know what your rhesus factor is if you are pregnant, for example. There are also potential links between different AB0 blood groups and your health.

Blood transfusions and blood donation

If you receive a blood transfusion, for example after losing a significant amount of blood, it is important that your body does not produce antibodies against the donated blood. Are you giving blood yourself? In that case, of course, you will not want a subsequent recipient to produce antibodies against your blood.

It is therefore useful to know your blood group and rhesus factor. After all, as we explained above, it is not just your AB0 blood group that is relevant when it comes to finding the right match; a person who is rhesus negative should also not receive blood from someone who is rhesus positive.


One of the first things a doctor will do if you become pregnant is determine your rhesus factor. There is a good reason for this, as if the mother is rhesus negative, problems can arise.

Even though, in principle, the bloodstreams of the mother and child are separate, in some cases a small amount of the baby’s blood can enter the mother’s system. If a rhesus-negative mother gets blood from her rhesus-positive baby in her own bloodstream, her body will produce antibodies. The mother will not be aware of this herself, but if these antibodies are passed on to the baby via the placenta, it is possible that they will break down the baby’s red blood cells. This will result in anaemia and possibly growth retardation. The risk is even higher in the event of a subsequent pregnancy, as the mother has already produced antibodies.

Fortunately, the rhesus factor is determined at an early stage of pregnancy, meaning that any measures can be taken if necessary. What’s more, a positive rhesus factor, which generally causes no problems, is the most common factor.

Blood groups and health

More and more research is being carried out into potential links between your blood group and certain health risks. Although your blood group has a much smaller effect than your genes, it may also be interesting to find out your blood group for this reason.

There are studies, for example, that suggest that blood group O, the most common blood group, is less often associated with stomach and pancreatic cancer than other blood groups. On average, people with blood group O also appear to be less susceptible to cardiovascular diseases. On the other hand, there are indications that people with blood group O are more susceptible to stomach ulcers.

It has been suggested that blood group AB is more often associated with cognitive decline than other blood groups. From time to time we have also read about a link between blood group AB and an increased risk of dementia or Parkinson’s disease, although there currently appears to be insufficient evidence to support this.

what is my blood group

How do you find out your blood group?

There are various ways to find out what your blood group is. Do you know your parents’ blood groups? If so, you may be able to deduce your own blood group from theirs. Other options are to take a blood or DNA test.

Your parents

If both of your biological parents have blood group O, you will also have this blood group. In the case of other blood groups it is impossible to say what your own blood group will be with any certainty.

Blood test

Have you ever had blood taken by a doctor? If so, your blood group may already be recorded in your medical file. Another way to find out your blood group is to donate blood. Your blood group will always be determined if you do this.

DNA test

One final way to find out what your blood group is (without the need for needles) is to take a DNA test. It is possible to tell what your AB0 blood group is with a reasonable degree of certainty from your DNA. Do you already have an iGene Passport? If so, you will also soon be able to see what your AB0 blood group is (for the time being the rhesus factor will not yet be shown in the app).

Incidentally, an iGene DNA test not only provides you with information about your blood group and all kinds of other personal traits. If you want to, you can also gain an insight into your genetic risks of developing certain conditions and find out your sensitivity to dozens of commonly used drugs.

Want to find out first if a DNA test is right for you? These 7 questions will help you decide!


Alexander KS, Zakai NA, Gileltt S, et al. ABO blood type, factor VIII, and incident cognitive impairment in the REGARDS cohort. Neurology 2014; 83: 1271-6.

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Chen, Z., Yang, S. H., Xu, H., & Li, J. J. (2016). ABO blood group system and the coronary artery disease: an updated systematic review and meta-analysis. Scientific reports, 6, 23250.

Edgren, G., Hjalgrim, H., Rostgaard, K., Norda, R., Wikman, A., Melbye, M., & Nyrén, O. (2010). Risk of gastric cancer and peptic ulcers in relation to ABO blood type: a cohort study. American journal of epidemiology, 172(11), 1280-1285.

Etemadi, A., Kamangar, F., Islami, F., Poustchi, H., Pourshams, A., Brennan, P., ... & Emadi, A. (2015). Mortality and cancer in relation to ABO blood group phenotypes in the Golestan Cohort Study. BMC medicine, 13(1), 8

Franchini, M., & Liumbruno, G. M. (2016). ABO blood group and neurodegenerative disorders: more than a casual association. Blood Transfusion, 14(2), 158.

Iodice, S., Maisonneuve, P., Botteri, E., Sandri, M. T., & Lowenfels, A. B. (2010). ABO blood group and cancer. European journal of cancer, 46(18), 3345-3350.

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