Causes of Anemia in Cats and How to Help
📝 Summary
Feline anemia falls into three mechanisms — reduced red-cell production, blood loss, and increased destruction — and the pattern (regenerative versus non-regenerative) guides the workup. From kidney failure and FeLV to parasites and onion toxicity, identifying the root cause is what turns supportive care into real recovery.
1 How Anemia Develops
Anemia comes from three broad groups: reduced red-cell production (usually non-regenerative), blood loss, and increased destruction. Loss and destruction typically trigger regeneration within 3–5 days of the insult, though chronic gastrointestinal bleeding causes iron deficiency and a non-regenerative picture.
2 Reduced Red-Cell Production
Bone-marrow damage is the usual cause. Kidney failure lowers erythropoietin, giving a normocytic normochromic anemia. Myelophthisis replaces marrow with tumor or fibrosis. Iron deficiency yields the classic microcytic hypochromic anemia. Inflammatory disease gives a mild-to-moderate normocytic normochromic anemia (packed cell volume often above 14–15%). The most common infectious cause is feline leukemia virus (FeLV); immune-mediated disease and toxins such as chloramphenicol or chemotherapy drugs also apply.
3 Blood Loss
Loss comes from gastrointestinal, urinary, or internal bleeding (e.g., splenic rupture, hemothorax) and may bring thrombocytosis and a high BUN-to-creatinine ratio. Causes include hereditary and acquired coagulation or platelet disorders (rodenticide poisoning, immune-mediated thrombocytopenia, liver disease), neoplasia (hemangiosarcoma, small-intestinal lymphosarcoma or adenocarcinoma), severe ulcerative gastroenteritis (eosinophilic gastroenteritis), trauma, feline lower urinary tract disease, and parasites — especially fleas and hookworms. Signs are petechiae, ecchymoses, nosebleeds, vomiting blood, melena, and hematomas; internal bleeding shows as a swollen abdomen or rapid breathing.
4 Increased Destruction (Hemolysis)
Primary immune-mediated hemolysis is rare in cats. Secondary immune-mediated hemolysis, usually from infection, is the most common cause. Hereditary red-cell defects (osmotic fragility, pyruvate kinase deficiency — especially in Somalis and Abyssinians) can be mistaken for immune-mediated disease. Hypophosphatemia from refeeding after anorexia or from insulin treatment of ketoacidosis triggers acute hemolysis. Oxidative toxins (acetaminophen, zinc, onion, garlic, some local anesthetics) form Heinz bodies; cats are more sensitive because their hemoglobin has more sulfhydryl groups. Microangiopathy damages red cells as they pass injured vessels, causing schistocytes.
5 Signs to Watch
Hemolysis shows splenomegaly, jaundice, hemoglobinemia, and hemoglobinuria. Cat red cells are smaller and paler than dogs’, so spherocytes are abnormal in cats and signal hemolysis.
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