Information about blood groups

Blood groups are a way of grouping blood types based on the characteristics of blood red cells and serum antibodies. ABO, Rh and Kell blood groups are determined for all blood donors.

Usually, patients need blood products in accordance with the general distribution of blood groups in Finland, because blood transfusion patients are primarily given blood that matches their own blood group. In other words, the most common blood groups A+ and O+ are used the most. Emergency blood, O-, is an exception because as the universal blood type, it can be given to all patients and is therefore given more often.

Blood groups vary across the population and have no impact on a person’s health.

What’s my blood group?

You can find out your blood group by donating blood. You do not need to know your blood group before you donate. The blood you donate is examined to find your blood group.

You will be informed of your blood group the next time you donate. You can also inquire about your blood group by calling the free donor information service on +358 (0)800 0 5801 from Mon–Fri 8.00am–5.00pm about two weeks after your donation.

The eight basic blood groups

Blood belongs to one of four ABO blood groups, i.e., to blood group A, B, O or AB. Each of these four blood groups is further classified according to the rhesus factor (rhesus D factor) into Rh D positive and Rh D negative.

  • There are eight basic blood groups in total: A+, A-, O-, O+, AB+, AB-, B- and B+.
  • The most common blood groups in Finland are A+ and O+. The least common among Finns is AB-

The ABO system is the most important and well-known method for defining a person’s blood group. In addition to this, there are also other blood group factors. Blood groups are groupings of blood types based on the characteristics of blood red cells and serum antibodies. In total, more than 35 other systems can be used to determine a person’s blood group.

Blood groups in Finland

In Finland, the most common blood group is A+ and the rarest is AB-. Blood groups in Finland are divided as follows:

  • Rh D positive blood groups: A+ 35%, O+ 28%, B+ 16%, AB+ 7%
  • Rh D negative blood groups: A- 6%, O- 5%, B- 2%, AB- 1%

Kell blood group

Of Finnish blood donors, 96% are Kell negative and 4% are Kell positive (i.e. positive for the K-antigen in the Kell blood group system).
K positive red blood cells can be given to anyone who needs blood, but a small percentage of K negative individuals will subsequently develop antibodies to the K antigen. Patients who have been diagnosed with anti-K antibodies should always be given K negative red blood cells.

The anti-K antibodies that have formed do not cause any problems in blood transfusions, since most (96%) donated blood is K negative. It is therefore not difficult to find K negative blood.

Antibodies, on the other hand, are significant during pregnancy. If a K negative mother has formed antibodies to the K factor and the foetus is K positive, the mother’s antibodies can cause the foetus’ blood cells to break down. For this reason, all girls and women of childbearing age are always given K negative red blood cells. The use of K negative blood products may also be considered for patients who receive repeated blood transfusions.

Donated K positive blood is given to patients just like K negative blood. 4% of Finns who need blood products are also K positive.

Rare blood groups

In addition to basic blood groups, people also have other blood group factors. Some of them are rare. Rarity can also manifest itself in such a way that a person does not have a blood group factor, which is very common in humans. Examples of rare blood groups are Jk-3, k neg, Vel neg and U neg.

Blood group factors other than ABO and Rh D may be important if, for example, a patient has developed antibodies against a particular blood group, or has to undergo repeated transfusions involving large amounts of blood.

Sometimes, international cooperation between the world’s blood services is a prerequisite for being able to help a patient.

Incompatible blood can endanger a patient

Receiving blood from a wrong blood group can cause a haemolytic reaction in a patient. The reaction occurs when the antibodies in the patient’s blood destroy the transfused red blood cells. This can cause various symptoms, such as fever and shortness of breath, and in the worst case the reaction can lead to kidney damage or even death.

In an emergency, patients are always first given red blood cells from the O Rh D negative blood group, as they are suitable for everyone. This is why O negative blood, also known as emergency blood, is needed more than other blood groups.

However, donors from all blood groups are needed every day. The hospital examines a patient’s blood group quickly, after which the patient receives red blood cells from their own blood group.

The table below shows which blood group can be given to which patient.

Blood groups and compatibilities

Patient’s blood group Donor’s blood group
O- O-
O+ O-, O+
B- B-, O-
B+ B+, B-, O+, O-
A- A-, O-
A+ A+, A-, O+, O-
AB- AB-, A-, B-, O-
AB+ AB+, AB-, A+, A-, B+, B-, O+, O-

Inheriting blood groups

Blood groups are a genetic characteristic, inherited from both parents. A child may therefore have a different blood group from their parent. For example, a child can inherit the gene for blood group O, even if their parent’s blood group is A. Sex plays no role in which blood group you inherit.

Paramedics rush from the ambulance. A man in a white t-shirt with O- in red font is standing next to him.

O negative is the emergency blood type

The Blood Service is looking for more blood type O Rh negative donors. O negative is the emergency blood type. It can save anyone of us.

Learn about emergency blood

How is blood screened

The most important thing for the patient receiving the blood is that the blood donor is healthy. The donor’s health is examined through the health questionnaire and laboratory tests performed on the blood samples.

Laboratory tests
Red blood cell products on a table with a blood product warehouse and a Blood Service employee in a white coat in the background.

What happens to donated blood?

Blood goes through many stages on its journey from donor to patient.

The journey of blood