Blood Type Compatibility Chart: Who Can Donate to Whom

Blood type compatibility decides who can safely receive blood from whom. It is not a formality: giving someone the wrong blood can trigger a severe, sometimes fatal immune reaction. Two ideas come up again and again — the universal donor (O-negative, for red cells) and the universal recipient (AB-positive). But there is a twist that surprises most people: for plasma, the rule flips completely. This guide walks through the ABO and Rh compatibility rules, gives you a plain who-can-give-to-whom chart, explains what "universal donor" and "universal recipient" really mean, and shows why a hospital lab still crossmatches every unit before it reaches your arm. It is part of our blood type hub.

Key takeaways

• Compatibility depends on antigens (markers on your red blood cells) and antibodies (in your plasma) from the ABO and Rh systems.¹
• Red blood cells: O-negative is the universal donor; AB-positive is the universal recipient.²
• Plasma is the mirror image: AB is the universal plasma donor, and O is the universal plasma recipient.²
• An ABO-incompatible transfusion can cause a hemolytic reaction, one of the most dangerous complications in medicine. Compatibility is never guessed — it is tested in the lab.³
• In practice, patients are usually given their own type (type-specific); O-negative is held for emergencies when the patient's type is unknown.²
• Beyond ABO and Rh, other antigens (Kell, Duffy, Kidd…) matter, which is why the lab runs an antibody screen and a crossmatch before releasing blood.⁴

How blood compatibility works

Every red blood cell is studded with antigens — molecular flags on its surface. The two systems that matter most for transfusion are ABO (which sorts you into A, B, AB, or O) and Rh (which makes you positive or negative, depending on the D antigen).⁵

Your plasma — the liquid part of blood — carries antibodies aimed at the ABO antigens you do not have. This is the key to the whole system. If you are type A, your plasma contains anti-B antibodies; if you are type B, it contains anti-A; type O has both; type AB has neither.⁶

Your ABO and Rh type is determined by a quick lab test called blood typing: technicians mix your red cells with anti-A, anti-B, and anti-D reagents and watch for agglutination (clumping), then confirm the result by testing your plasma against known cells.⁷ It's the same test done on every donated unit and every prospective transfusion recipient.

Now put the two together. If a patient receives red cells carrying an antigen their plasma is primed to attack, those antibodies latch onto the transfused cells and destroy them. That is a hemolytic transfusion reaction — the immune system shredding the very cells meant to help — and it can cause fever, kidney failure, shock, and death.³ So the golden rule of transfusion is simple: never introduce an antigen the recipient's plasma will attack. Everything below follows from that one idea.

Red-cell compatibility chart

For red blood cell transfusions, what counts is not adding an A or B antigen the recipient cannot tolerate. Here is who can receive red cells from whom, on the ABO axis:²

Read the other direction, it becomes a donation chart:

Notice the pattern: O gives to everyone but can only receive O, while AB receives from everyone but can only give to AB. They are perfect opposites — one is the ultimate giver, the other the ultimate taker. Rh has to be layered on top of this (covered below), which is why the real-world matrix has eight types, not four.

The universal donor and universal recipient

Two types anchor the whole chart.

O-negative is the universal red-cell donor. Its cells carry no A, no B, and no D antigen, so there is nothing for any recipient's antibodies to attack. That is why emergency rooms and ambulances stock O-negative for trauma and situations where there is no time to type the patient.² Because it is so widely useful — and relatively uncommon — O-negative is a constantly in-demand blood type. We cover it in depth in the dedicated guide on the universal blood donor.

AB-positive is the universal recipient. It carries A, B, and D antigens and has no anti-A or anti-B antibodies in its plasma, so it can accept red cells from any ABO/Rh type without an ABO reaction.⁵ AB-positive patients are the easiest to match for red cells — but, as you're about to see, that advantage reverses for plasma.

These labels are handy but simplified. Hospitals don't hand O-negative to everyone by default: the supply is limited, and using type-specific blood conserves it. And "universal" only ever refers to the ABO and Rh antigens — it does not account for the dozens of minor blood-group antigens a crossmatch is designed to catch.⁴

Plasma is the opposite

Here is the twist that trips people up. Plasma carries the antibodies, not the red-cell antigens — so its compatibility rule runs backwards.²

• AB plasma contains neither anti-A nor anti-B, so it can be given to anyone. AB is the universal plasma donor.
• O plasma contains both anti-A and anti-B, so it can only go to O recipients — but O can safely receive plasma from any type. O is the universal plasma recipient.

So the same person is a universal donor in one product and a universal recipient in another. Remember it as a clean flip:

This matters clinically because whole blood is almost always split into components — red cells, plasma, and platelets — each transfused separately and each matched by its own rule.⁸ Platelets sit in between: they carry weak ABO antigens and float in a small amount of plasma, so blood banks prefer ABO-matched platelets when available but will cross ABO lines when supply is tight, because platelet shelf life is only about five days.⁹

Rh compatibility

Layered on top of ABO is the Rh system, named for the D antigen. If you have D on your red cells you are Rh-positive; if not, Rh-negative.¹ The rule for red cells:

• Rh-negative recipients should receive only Rh-negative red cells. If Rh-negative blood is exposed to the D antigen, the immune system can make anti-D antibodies — a process called alloimmunization — which causes trouble with future transfusions.
• Rh-positive recipients can receive either Rh-positive or Rh-negative red cells.

Rh matters most in two settings: transfusion and pregnancy. An Rh-negative person who makes anti-D can react to future Rh-positive units, and an Rh-negative mother carrying an Rh-positive baby can develop antibodies that threaten a later pregnancy — the reason Rh-negative expectant mothers are offered Rh immune globulin.⁵ For the full picture, see our guide on the Rh factor.

Why crossmatching still matters

If the charts are this clear, why does the hospital lab still run tests on every unit? Because ABO and Rh are only the beginning. Human blood carries dozens of other antigen systems — Kell, Duffy, Kidd, MNS, and more — and a patient who has been transfused before or pregnant may have quietly developed antibodies against one of them.¹

That is why, before a planned transfusion, the lab performs a type and screen followed by a crossmatch:⁴

1. ABO/Rh typing — confirming the patient's type on a fresh sample.
2. Antibody screen — testing the patient's plasma against known red cells to detect antibodies to minor antigens.
3. Crossmatch — physically mixing the patient's plasma with the intended donor cells to confirm they don't react.

For patients who need frequent transfusions — those with sickle cell disease or thalassemia, for example — labs increasingly turn to blood group genotyping. Instead of testing one antigen at a time with reagents, genotyping reads the DNA to predict many red-cell antigens at once, making it easier to find deeply matched donors and to reduce the alloimmunization that repeat transfusions otherwise cause.¹⁰ It's a good illustration of the bigger point: "compatible" means far more than sharing an ABO letter and a plus or minus sign.

Crucially, the most common cause of a fatal ABO-mismatch reaction is not a lab typing error — it's a clerical mistake: the wrong patient wristband, a mislabeled tube, or a unit hung on the wrong bed.⁴ This is why every step is double-checked at the bedside. Compatibility is a laboratory and medical decision, established by testing — never something to work out on your own from a chart.¹¹ To understand how a transfusion actually proceeds from order to bedside, see our guide on blood transfusion.

Get your blood work interpreted by AI DiagMe

Compatibility itself is decided by the lab and your physician. But understanding your own blood type, your Rh factor, and how your results fit together helps you have a clearer conversation with your care team.

👉 AI DiagMe interprets your lab results — blood, urine, or stool — in plain language, taking your whole profile into account. An informational service that does not provide a diagnosis and complements, never replaces, your physician.

Frequently asked questions

Bottom line

Blood type compatibility keeps transfusion safe. For red blood cells, O-negative is the universal donor and AB-positive is the universal recipient; for plasma, the rule flips — AB donates to all, O receives from all. These labels are useful shorthand but simplified: in real medicine, patients get type-specific blood, the lab screens for other antibodies, and every unit is crossmatched and double-checked at the bedside. Compatibility is always confirmed by testing, never guessed. To go further, start with the blood type hub, then read about the universal blood donor and the Rh factor.

Sources

Official U.S. sources and peer-reviewed publications (PubMed) used for this guide: