Vet’s 2025 Guide to Polycythemia in Dogs 🩸 Diagnosis, Treatment & Care

By Dr. Duncan Houston BVSc

💡 Introduction

Polycythemia—also known as erythrocytosis—is a condition where a dog’s blood becomes overly thick due to increased red blood cell count or volume, leading to sluggish circulation and risk of clotting.

1. Understanding the Types of Polycythemia

1.1 Relative (Spurious) Polycythemia

Occurs when there's normal red blood cell mass but reduced plasma—often due to dehydration, heatstroke, fluid loss, or stress.

1.2 Absolute Polycythemia (Erythrocytosis)

• Primary (Polycythemia vera): a rare bone marrow neoplasm causing uncontrolled RBC production.
• Secondary: increased red cell production triggered by either low oxygen (heart/lung disease, high altitude) or inappropriate erythropoietin from kidney tumors or endocrine conditions.

2. Mechanisms & Consequences of Thick Blood

Elevated hematocrit (>60–65%) increases blood viscosity, hampering oxygen delivery and promoting complications like hypertension, clot formation, tissue hypoxia, seizures, and even blindness.

3. Clinical Signs to Watch

• Lethargy, exercise intolerance, weakness.
• Bright red mucous membranes, ruddy skin tone.
• Increased thirst/urination.
• Neurological signs: seizures, ataxia, blindness.
• Bleeding tendencies—nosebleeds, GI blood.
• Heart murmur, respiratory distress.

4. Diagnosing Polycythemia in 2025 🧪

• Complete blood count (CBC) to confirm high PCV, RBC, & hemoglobin.
• Fluid trial to differentiate relative vs absolute type.
• Measure erythropoietin (EPO) to distinguish primary from secondary.
• Thoracic imaging, abdominal ultrasounds, heart echo to rule out hypoxic disease or EPO-secreting tumors.
• Bone marrow aspirate may be needed for suspected polycythemia vera.

5. Treatment Strategies ❤️

5.1 Relative Polycythemia

Managed with rehydration via IV fluids and addressing underlying fluid loss.

5.2 Absolute Polycythemia

• Phlebotomy: frontline therapy—remove ~10–20 mL/kg blood while replacing fluids to reduce hematocrit to 50–60%.
• Hydroxyurea: a myelosuppressive drug to reduce bone marrow RBC output; monitor CBC regularly for side effects.
• Alternate agents: chlorambucil may be used if hydroxyurea is not tolerated.
• Treat underlying cause: manage heart/lung disease, remove tumors, adjust medications that elevate EPO.

6. Ongoing Monitoring & Prognosis

• Frequent CBCs during initial treatment (weekly to monthly).
• Track clinical signs—thirst, bleeding, behavior, neurologic changes—via the Ask A Vet app.
• Prophylactic anticoagulation may be considered if clotting risk is high.
• Prognosis varies: relative forms often resolve once cause is treated; primary and secondary require long-term management; median survival 12–36 months on hydroxyurea.

7. Home Care & Client Support 🏡

• Maintain hydration—offer fresh water and wet food regularly.
• Monitor for lameness, bleeding, neurological signs—report any immediately.
• Home phlebotomy visits or clinic-based sessions to control PCV.
• Use Ask A Vet app for symptom logging, appointment reminders, and direct photo sharing.

🔍 Key Takeaways

• Polycythemia is rare but serious; early detection preserves quality of life.
• Differentiate spurious (fluid loss) from true polycythemia via fluid therapy and testing.
• Phlebotomy and hydroxyurea are effective treatments; treating the underlying disease is essential.
• Regular bloodwork and home monitoring prevent complications like thrombosis.
• With proper care, many dogs live well for months to years after diagnosis.

🩺 Conclusion ❤️

Polycythemia in dogs ranges from temporary fluid shifts to complex bone marrow disorders. In 2025, accurate diagnosis, targeted phlebotomy, and supportive medications—guided by detailed monitoring and digital support like Ask A Vet—allow dogs to thrive despite this blood disorder. 🐶✨

Dr Duncan Houston BVSc – committed to harmonizing advanced hematology care with compassionate, owner-friendly follow-up.

Visit AskAVet.com and download the Ask A Vet app for treatment tracking, blood monitoring reminders, and expert support through every phase of polycythemia care. ❤️