Dog Blood Types: DEA 1, Universal Donors and Transfusions

Dogs have more than a dozen blood groups, named DEA (dog erythrocyte antigen) plus a number. The one your vet checks before a transfusion is DEA 1: every dog is either DEA 1-positive or DEA 1-negative. DEA 1-negative dogs are the "universal donors" blood banks look for, and most DEA 1-positive dogs can safely receive either type.

That one label also explains why a dog's second transfusion is riskier than its first, and why some breeds get recruited as blood donors more than others.

Do Dogs Have Blood Types?

Yes. A blood type is set by antigens, small combinations of proteins and sugars on the surface of red blood cells. A dog either has a given antigen (positive) or lacks it (negative). Each blood group is inherited on its own, so one dog can carry many different combinations.

The Merck Veterinary Manual lists these recognized groups:

DEA 1: Positive vs Negative

DEA 1 is the blood group vets care about most because it is the one most likely to trigger a strong immune response. How common it is depends on where you look: Merck puts DEA 1-positive dogs at roughly 33-65% depending on the region, and a UC Davis study of 6,469 dogs in California found 61.2% were positive.

You may still see DEA 1.1, 1.2 and 1.3 on older pages. Researchers now explain those old subtypes as differences in how much of the same antigen a dog carries, so labs report DEA 1 as:

• Negative: no DEA 1 antigen.
• Weak positive: a small amount.
• Positive (2+ to 4+): moderate to strong.

For practical purposes, "DEA 1.1" on an older blood bank page means DEA 1.

The reason it matters: a DEA 1-negative dog that receives DEA 1-positive blood can make antibodies against it, and those antibodies can destroy positive blood the next time.

Universal Donors and Universal Recipients

In people, O-negative blood is the universal red cell donor. In dogs, the closest match is DEA 1-negative blood: it can go to a DEA 1-negative or a DEA 1-positive dog without the risk of DEA 1 sensitization.

• DEA 1-negative dogs are the universal donors. Donor programs such as Kansas State's actively look for them.
• DEA 1-positive dogs are the universal recipients. They can receive positive or negative blood, though blood banks give positive blood to positive dogs when they can, which saves negative units for the dogs that need them.
• Weak-positive dogs are the exception. Merck advises that a weak-positive dog who needs blood should get DEA 1-negative blood, while a weak-positive donor is treated as positive.

Some blood banks use a stricter definition: a "universal donor" is negative for every DEA group tested except DEA 4. In an Ohio State study of retired racing Greyhounds, 57.3% met that stricter bar, compared with 28% of other dogs screened as donors.

Do Dogs Have Blood Types Like Humans?

Not quite. People have four main ABO groups (A, B, AB and O), and each one is Rh-positive or Rh-negative, which gives the eight common human blood types. Dogs use a different system (DEA), with more groups.

The bigger difference is in the immune system. Dogs generally don't carry meaningful natural antibodies against blood types they lack. Researchers at the University of Pennsylvania's animal blood bank found no clinically significant antibodies in dogs that had never been exposed to foreign blood, and none of the 137 dogs tested in the Greyhound study had them either. So a first mismatched transfusion usually doesn't cause an immediate reaction. It can, however, prime the immune system for next time.

Cats are the opposite: they do carry natural antibodies, so a cat must be blood typed before even a first transfusion. (More on why cats need blood in our guide to anemia in cats.)

Breeds More Often DEA 1-Negative (and Positive)

Breed studies tell you which dogs are more likely to be DEA 1-negative, which is why blood banks recruit some breeds more than others. They can't tell you your own dog's type. Only a blood test does that.

This is one reason retired racing Greyhounds are popular donors: most are DEA 1-negative, and many are negative for the other tested groups too.

Dal: Why Dalmatians and Dobermans Need Extra Typing

The Dal blood group was discovered when a Dal-negative Dalmatian was sensitized by a transfusion. About 98% of dogs are Dal-positive, but a North American study found Dal-negative blood in 42.4% of Doberman Pinschers, 11.7% of Dalmatians and 12 of 21 Shih Tzus tested (with occasional Lhasa Apsos and Bichon Frises too).

Because nearly every donor is Dal-positive, a Dal-negative dog can be sensitized by its first transfusion and react to the next one. The study authors recommend extended Dal typing in these breeds, and whenever a dog has problems after earlier transfusions.

First Transfusion vs Later Transfusions

Here is how vets keep transfusions safe, in the order it happens.

1. Blood typing for DEA 1. Merck's current guidance is to type every donor and every recipient for DEA 1 before a transfusion, first transfusion included. Clinics can do this in-house with a typing card.
2. Matching the blood. A DEA 1-negative dog gets DEA 1-negative blood, which keeps future transfusions possible.
3. Crossmatching for any dog transfused before. A crossmatch mixes the recipient's blood with the donor's in the lab to look for a reaction. Typing only checks DEA 1; a crossmatch checks for antibodies against any blood group, including ones nobody tested for. Merck recommends one for any dog that had a transfusion more than 4 days earlier.
4. Extra typing where it matters. Dal typing for Dobermans, Dalmatians and Shih Tzus.

Why the second transfusion is the risky one: after a mismatched first transfusion, the dog builds antibodies over the following days. The Penn blood bank team notes this can cause a delayed reaction (the donated cells die off early) in as little as a week. A later transfusion of the same mismatched type meets antibodies that are already waiting, and that reaction can be life-threatening.

Why Would My Dog Need a Blood Transfusion?

A transfusion replaces blood or blood parts a dog has lost or can't make fast enough. Signs of severe anemia include pale gums, a fast heart rate, weakness, low energy and, after sudden blood loss, collapse or shock. When red cells are being destroyed, the gums and whites of the eyes can turn yellow. Any of these needs a vet the same day; collapse needs one now.

Common reasons, according to the Merck Veterinary Manual:

• Blood loss: injury, surgery, a bleeding tumor (for example on the spleen), stomach ulcers, clotting disorders, rat poison, and heavy parasite loads such as hookworms in puppies or severe flea infestations.
• Red blood cells being destroyed: immune-mediated hemolytic anemia (IMHA), the most common cause in dogs; tick-borne infections such as ehrlichiosis and babesiosis; and toxins such as onions and zinc.
• Not enough red cells being made: long-term kidney disease, bone marrow disease, and some chronic illnesses (these usually cause milder anemia).

Dogs with clotting disorders may need repeated transfusions of whole blood, red cells, plasma or platelets, which is exactly when typing and crossmatching matter most.

What Happens During a Transfusion

1. The vet decides a transfusion is needed based on how the dog looks and is coping, not on one lab number. A dog doesn't need a normal red cell count to be stable.
2. Typing, matching and crossmatching happen as described above.
3. The vet chooses the blood product: whole blood, packed red cells or plasma, depending on the problem. The vet works out how much the dog needs.
4. An IV line goes in. Blood runs through its own line with a special filter. Many clinics start with a small test amount and watch for a reaction before continuing.
5. The team watches the dog closely, checking vital signs often in the first hour and again over the following day.

A dog in shock gets blood quickly; a stable dog usually gets it more slowly, often over about four hours, and dogs with heart or kidney disease more slowly still.

A transfusion buys time. It doesn't fix the reason the dog needed blood, so your vet will also look for the cause and treat it.

Risks, Recovery and What to Watch For

Merck's pet owner guide says most transfusions are safe and effective. The reactions the team watches for:

• Fever, one of the most common reactions, often mild.
• Hemolytic reaction: the donated red cells are destroyed, either by antibodies (a mismatch) or because the blood was damaged in storage or handling. Signs range from fever and a fast heart rate to shock. A delayed version can show up more than a day later, often only as a falling red cell count.
• Allergic reaction: hives, swelling or vomiting. Anaphylaxis is the severe form and can cause shock.
• Fluid overload, which shows as breathing trouble during or within a day of the transfusion.
• Infection from contaminated blood, and low calcium from the preservative in stored blood.

Recovery depends far more on the underlying cause than on the transfusion. IMHA, for example, is serious: Merck reports that 20% to 75% of affected dogs die from it.

Call your vet after you get home if your dog seems weak, has pale or yellow gums, breathes fast or hard, vomits, develops hives or swelling, or just seems off. Keep any recheck appointments, because a delayed reaction may only show on a blood test.

How Dogs Become Blood Donors

Many veterinary blood banks rely on volunteer donors: pet dogs whose owners bring them in every couple of months. Veterinary school hospitals run many of these programs (Colorado State's supplies over 700 transfusions a year for dogs and cats), and so do some emergency and specialty hospitals.

Criteria vary by program. Here is what four US programs ask for:

Before a dog is accepted, programs do a physical exam, blood typing, routine bloodwork and screening for blood-borne infections, guided by an ACVIM consensus statement. Programs looking for universal donors favor DEA 1-negative dogs, but positive dogs are needed too.

On donation day, a vet examines the dog before every draw and a licensed vet tech collects the blood. Most dogs are cooperative; Colorado State says a mild sedative may be discussed for dogs too wiggly to stay still. Dogs go home the same day. Virginia Tech suggests a harness for the ride home (so a collar doesn't rub the draw site), a quiet rest of the day, and normal activity the next day.

How often? About every 8 to 12 weeks at Colorado State, and about every two months at Kansas State. In return, donors typically get yearly checkups and bloodwork, infectious disease screening, and flea, tick and heartworm prevention, and at some programs a bag of food after each donation.

If your dog fits the profile, ask your vet whether a local hospital runs a donor program.

Questions to Ask Your Vet

• Does my dog need to be blood typed or crossmatched before this transfusion?
• Is my dog DEA 1-negative, positive or weak positive?
• My dog is a Doberman, Dalmatian or Shih Tzu. Should we test for Dal too?
• What signs should I watch for at home, and when is the recheck?
• Is there a blood donor program near us, and would my dog qualify?

Originally written by Dr. Kaylee Ferreira. Updated by the I Love Veterinary editorial team.

Sources

• Merck Veterinary Manual: Blood Groups in Dogs and Cats
• Merck Veterinary Manual: Blood Transfusions in Dogs and Cats
• Merck Veterinary Manual (pet owner): Blood Groups and Blood Transfusions in Dogs
• Merck Veterinary Manual (pet owner): Anemia in Dogs
• VIN, Penn Animal Blood Bank: Canine and Feline Blood Types and Blood Compatibility Issues
• Iazbik et al., Vet Clin Pathol 2010: Prevalence of dog erythrocyte antigens in retired racing Greyhounds
• Bank et al., J Vet Emerg Crit Care 2023: Prevalence of DEA 1 in dogs tested in California
• Carli et al., BMC Vet Res 2017: Frequency of DEA 1 antigen in 1037 dogs in Italy
• Goulet et al., J Vet Intern Med 2017: Prevalence and inheritance of the Dal blood group in North America
• Véran and Blais, J Vet Intern Med 2023: Cage-side card for Dal blood typing
• Wardrop et al., J Vet Intern Med 2016: ACVIM update on blood donor screening for blood-borne pathogens
• Virginia Tech Veterinary Teaching Hospital: Blood Bank
• Colorado State University Veterinary Teaching Hospital: Veterinary Blood Bank
• Kansas State Veterinary Diagnostic Laboratory: Canine Blood Donor Program
• VCA Alameda East Veterinary Hospital: Blood Bank
• American Red Cross: Blood Types

This article is for general information and is not a substitute for advice from your veterinarian.