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Blood Groups

MaryN just asked an question on the forums about Blood Groups which made me realise that I had forgotten mine and also couldn’t remember what Blood Groups were compatible with others. It is an area of great interest containing areas of concern and is more than knowing your blood group and looking at a chart which is an impression we all have.

The following article has been pulled together with information from several sources and should be validated before use. Survival UK bears no responsibility if you use this information without medical advice. It is intended as starter information only and if there are medical facilities available you should use those rather than try anything yourself. This is information intended only for aid after an event when no other options are available.

A blood group is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system. Some of these antigens are also present on the surface of other types of cells of various tissues. Several of these red blood cell surface antigens can stem from one allele (or an alternative version of a gene) and collectively form a blood group system. Blood types are inherited and represent contributions from both parents. A total of 35 human blood group systems are now recognized by the International Society of Blood Transfusion (ISBT). The two most important ones are ABO and the RhD antigen; they determine someone’s blood type (A, B, AB and O, with +, − or Null denoting RhD status).

ABO blood group system


Phenotype Genotype
A AA or AO
B BB or BO

Rh blood group system

The Rh system (Rh meaning Rhesus) is the second most significant blood-group system in human-blood transfusion with currently 50 antigens. The most significant Rh antigen is the D antigen, because it is the most likely to provoke an immune system response of the five main Rh antigens. It is common for D-negative individuals not to have any anti-D IgG or IgM antibodies, because anti-D antibodies are not usually produced by sensitization against environmental substances. However, D-negative individuals can produce IgG anti-D antibodies following a sensitizing event: possibly a fetomaternal transfusion of blood from a fetus in pregnancy or occasionally a blood transfusion with D positive RBCs. Rh disease can develop in these cases. The presence or absence of the Rh(D) antigen is signified by the + or − sign, so that for example the A− group is ABO type A and does not have the Rh (D) antigen.

Other blood group systems


Blood Plasma

Just to complicate things a bit more there is Blood Plasma. Blood plasma is the pale yellow liquid component of blood that normally holds the blood cells in whole blood in suspension; this makes plasma the extracellular matrix of blood cells. It makes up about 55% of the body’s total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells). It is mostly water (up to 95% by volume), and contains dissolved proteins (6–8%) (i.e.—serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na+, Ca2+, Mg2+, HCO3−, Cl−, etc.), hormones, and carbon dioxide (plasma being the main medium for excretory product transportation). Plasma also serves as the protein reserve of the human body. It plays a vital role in an intravascular osmotic effect that keeps electrolytes in balanced form and protects the body from infection and other blood disorders.

Blood Banks

Before an event we have blood banks that take donors blood, type all the components and store it or process it. when it is processed the plasma and other components are separated in a centrifuge and stored separately. This leaves much of the blood usable with simple checks as most of the antigens are separated out. Currently we can ensure that the correctly matched blood type or plasma is given to the recipient after we have screened anything we don’t like out of the donor blood.

Red blood cell compatibility


If a patient in a hospital situation needs a blood transfusion in an emergency, and if the time taken to process the recipient’s blood would cause a detrimental delay, O negative blood can be issued. Because it is compatible with anyone, O negative blood is often overused and consequently is always in short supply. According to the British Chief Medical Officer’s National Blood Transfusion Committee, the use of group O RhD negative red cells should be restricted to persons with O negative blood, women who might be pregnant, and emergency cases in which blood-group testing is genuinely impracticable.

Red blood cell compatibility chart


Red blood cell compatibility table
Recipient Donor
O− Green tickY Red X
Red XN Red XN Red XN Red XN Red XN Red XN
O+ Green tickY Green tickY Red XN Red XN Red XN Red XN Red XN Red XN
A− Green tickY Red XN Green tickY Red XN Red XN Red XN Red XN Red XN
A+ Green tickY Green tickY Green tickY Green tickY Red XN Red XN Red XN Red XN
B− Green tickY Red XN Red XN Red XN Green tickY Red XN Red XN Red XN
B+ Green tickY Green tickY Red XN Red XN Green tickY Green tickY Red XN Red XN
AB− Green tickY Red XN Green tickY Red XN Green tickY Red XN Green tickY Red XN

Table note

Plasma compatibility

Blood plasma compatibility is the inverse of red blood cell compatibility. This is because the antibodies responsible for adverse reactions are carried in the plasma: type AB plasma carries neither anti-A nor anti-B antibodies and can be transfused to individuals of any blood group; but type AB patients can only receive type AB plasma. Type O carries both antibodies, so individuals of blood group O can receive plasma from any blood group, but type O plasma can be used only by type O recipients.

Plasma compatibility chart

Plasma compatibility table
Recipient Donor
O Green tickY Green tickY Green tickY Green tickY
A Red XN Green tickY Red XN Green tickY
B Red XN Red XN Green tickY Green tickY
AB Red XN Red XN Red XN Green tickY

Table note
1. Assumes absence of strong atypical antibodies in donor plasma


Just to complicate things even more



What happens when I need a transfusion now?

If we watch what goes on now. In the event of a requirement for a transfusion the first thing they do is type the blood. In the event of an emergency they use plasma or O type blood in you until they get your type. Remember that all the antigens are processed out so this is as clean as you can get. Then they will use your own blood type when it is identified.

Out in the field, or in some of the hellholes around the world with little or no medical facilities, in an emergency they are forced sometimes to just plug someone into someone else simply with knowing their ABO and Rh blood group systems and using a simple needle set ignoring the other blood group systems. This is more like an event situation where we don’t have access to screened blood and death will be the alternative. It can lead to death but they were going anyway and this is a last ditch attempt to help them.

What does this mean for me after an event?

When someone needs blood you will need to know what blood is compatible with them and who can provide that blood type. Unless you have prepped well you won’t have any available plasma or whole blood outside what is in your bodies as blood banks will not be practical after a major event. You will not have any way of testing it either in the heat of the moment.

With a bit of luck your family groups should all be compatible and you are more likely to know their medical history. This will be valuable in finding the right donors.

With 35 blood group systems and 50 antigens there is a lot to consider although the main ones which are critical for transfusions are the ABO and Rh blood group systems. The others are less important but may have adverse effects if the donor is incompatible with the recipient. Unfortunately as we will be unable to screen for these we will simply be going with the odds and using the main ABO and Rh blood group systems. There will be issues with some donors and recipients. It can’t be helped which is why we must never do this unless there are no other options.

If you have the capabilities you will be able to extract and store blood. You may also be able to separate the plasma and the whole blood and store those for 40 days if the temperature is kept about 4oC. Most of us will not have the capability for that after an event and the best we could do is to extract blood and process it as it is required without any storage or processing. The only advantage of being able to extract and store blood is if you are going to perform some surgery for example or are expecting a fight and want to stock up just in case. Blood is sterile when extracted but like everything contact with the outside contaminates it and the sooner used the better, even if stored. Currently blood is treated with antibiotics before storage. That again is unlikely in our world after an event so blood storage increases risk of infection.

What should I do next?

  • Create a medical file for every member of your group
  • Make a note of the blood group for everyone in your group
  • work out who can provide transfusions for everyone else. Record that information in the medical file.
  • Purchase some transfusion kits for your medical kits
  • Ensure the blood type compatibility info, and names, are with that kit
  • Hope you never have to use it.

3 comments to Blood Groups

  • Fred

    So the poor sod with “O” type is going to be in demand. My type is no use to anyone except my type.

  • Wasn’t really expecting to find this sort of post on your site, but I’m glad I did! I’m actually a Clinical Laboratory Scientist by profession, and the information you have on here is very helpful especially to those who have zero knowledge on it. Great sharing these! Oh, have you heard of Rhogam for RH negative blood types?

  • Ysbryd

    I’m group O+ ………not quite a universal doner.

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