Anemia Due to Enlarged Blood Cells in Dogs

PetMD Editorial
By PetMD Editorial on Aug. 12, 2008

Anemia, Megaloblastic (Anemia, Nuclear Maturation Defects) in Dogs


In this disease, red blood cells fail to divide and become abnormally large. These cells are also deficient in necessary DNA material. These giant cells with underdeveloped nuclei are called megaloblasts, or “big cells.” Red blood cells are mainly affected, but white blood cells and platelets can also go through changes.

Giant schnauzers seem to have an inherited tendency to have this kind of anemia. In dogs, it is generally mild, and left treated. The seriousness of the anemia can range from mild to severe. This disease is genetic in Toy Poodles, but it does not require treatment.

The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.

Symptoms and Types


  • Deficiencies of Vitamin B-12 and folic acid
  • Leukemia
  • Bone marrow disorder
  • Genetics
  • Drugs such as chemotherapy


Tests will be conducted to rule out the following:

  • All mild to moderate non-regenerative anemias, including those of inflammatory disease, renal disease, and lead poisoning
  • Complete blood counts will be taken and bone marrow aspiration analysis

Complete blood count, biochemistry, and urinalysis will examine the following:

  • Is the anemia mild or moderate?
  • Is the anemia caused by over-sized cells?
  • Bone marrow biopsy usually reveals if there are an abnormal amount of cells



Once the underlying cause is identified, a treatment plan will be developed to deal with that particular illness first. This is a relatively mild disease. Treatment will be administered on an outpatient basis. If animals are demonstrating signs of drug toxicity, discontinue the offending drug. Instead, supplement your dog's diet with folic acid or vitamin B12. Giant schnauzers should get injections of vitamin B-12 every few months.


Living and Management

Initially, you should take your pet in to see the veterinarian weekly for a complete blood count, and occasionally for a bone-marrow aspiration and evaluation.

Ultimately, your pet's prognosis will depend on the underlying cause of the anemia. If a drug was the cause for the anemia, taking your pet off the drug should resolve the problem.

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