In biology classes at school I was taught that O can be a donor to all blood types (given matching Rh group and other details), and AB can receive transfusion from any type. Quick googling seems to suggest this is true, at least theoretically for example, Wikipedia

However, I recently came across a discussion thread (in Facebook) where more than one person (at least one of them went for internship as nurse) claims that this is only true in theory, in practice transfusion is only allowed for exact same blood type (e.g. AB can only receive from AB). And once in a while I receive chain message from friends saying something like "My relative is in emergency, need AB donor urgently" (or need A donor, or need B donor) despite they should be able to find O which is the most common blood type.*

Can I find an authoritative reference that mentions universal donor transfusion is regularly done without any problem, and the "universal donor" concept isn't just theoretical?

*All these discussions and chain messages happen in Indonesia.

  • 1
    Using comments to attempt to answer the question is not appropriate. Use the comments to discuss technical issues with the question only. We will lock the question if comments get abused further.
    – Sklivvz
    Commented Aug 6, 2014 at 23:33

3 Answers 3


The Australia and New Zealand Society of Blood Transfusion has published a document entitled Guidelines for the Administration of Blood Products, which specifically deals with recommended practice for transfusions, rather than simply biological theory. Section 5.4 is entitled "Emergency red cells" and states:

In critical bleeding, and at the discretion of the treating clinician, there may be insufficient time to undertake full compatibility testing. It may be necessary to provide emergency group O red cells which may not be specifically labelled for the patient.

The decision to use uncrossmatched blood components must balance the patient’s clinical need against the risk of potential adverse events such as a transfusion reaction due to pre-existing antibodies.

This makes it clear that transfusion with type O red cells is accepted practice when it is not possible to test the patient's blood type; but that matched blood types are preferred when circumstances allow. So this is one sense in which type O can be used as a universal donor.

As comments below and other answers point out, transfusions of whole blood and plasma are a different story.

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    Not directly relevant, but I'm curious now if a matched blood type preferred when allowed because it is better for the patient, or because you wouldn't want to waste the limited type O resource?
    – Mr.Mindor
    Commented Aug 6, 2014 at 19:21
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    @Mr.Mindor: There are some gene defects that make it impossible for some people to receive type O, and some kell rhesus,mn,duffy etc. factor combos that make it unpleasent to dangerous to blindly receive O.
    – PlasmaHH
    Commented Aug 6, 2014 at 20:16
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    You used instructions concerning red cells and drew conclusions about (whole) blood. This is wrong; see Sean's answer for why.
    – Ben Voigt
    Commented Aug 7, 2014 at 18:03
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    @Mr.Mindor Both things are important. Remember that 0 RH- is quite uncommon in many places (1:50 in Czechia for instance, while equal distribution would give 1:8). As well, it is better to transfuse as precise blood as possible to avoid possible rejective reaction of the organism, as explained by others.
    – yo'
    Commented Aug 8, 2014 at 10:12

The central problem is differentiating transfusion of whole blood, red blood cells, and plasma. Traditionally, when people speak of "blood types", they're discussing their Red Blood Cell type. The plasma contains its own factors, which are generally opposite to that of the red blood cells. Thus, O- is a universal donor for RBC donations and AB+ for plasma. Plasma works the other way around. For whole blood transfusion, an exact match is necessary to avoid transfusion issues, although, as noted above, transfusion issues are considered to be a lesser problem than the blood loss in emergency situations. Since most modern blood blanks separate the RBC and plasma components, and re-mix them as necessary for transfusion, and the risks are higher for RBC incompatibility, the idea of O- being the universal donor is a handy shorthand.


It's true that what is valid for packed red blood cell concentrates is not always valid for whole blood. However, if you want a practical real-life answer, we actually do keep O- packed red blood cell concentrates as an emergency decentralized reserve in operating theaters and emergency departments.

So in summary:

  • O negative is a universal donor in real-life practice
  • AB positive is a universal receiver (since giving rhesus + blood to a rhesus - patient could potentially cause a harmful transfusion reaction)
  • Those 2 propositions above are a shortcut in the sense that blood contains a multitude of different antigens, not only ABO and rhesus factor. However, in an overwhelming majority of cases those propositions are valid because most other antigens ("minor antigens") usually do not lead to clinically significant transfusion reactions even when mismatched (see below, and here)

One other issue that has not been discussed here, is that the patient's blood may also contain "irregular antibodies", which are routinely searched for before any whole blood-derived product transfusion (platelets, plasma, etc.). Those antibodies can appear as a consequence of a contact between the patient's organism and an external blood product, such as in the case of a history of multiple blood transfusions, or even by immunization of the mother against her child's blood from contact during labor. That is the reason why only having blood group and rhesus is not enough for what is considered "safe" transfusion nowadays. In my hospital for instance, we are required to have the patient tested for irregular antibodies, and that test must not be more than 96h old for transfusion in a non-immediate life threatening context. Untested O- packed red blood cells are left as a last resort, in case we do not have time to perform the required tests.

Oh, and here is a good authoritative reference on transfusion safety, if you want statistics.

  • 1
    On this site we only accept answers based on factual references (e.g. scholarly articles). Please add references to your answer.
    – Sklivvz
    Commented Aug 8, 2014 at 18:46
  • 2
    What you say sound totally correct. But the rules here demand references to reliable sources. Please add them so we don't lose a good answer.
    – matt_black
    Commented Aug 8, 2014 at 22:51

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