Polycythemia in Cats: A Vet’s 2025 Guide to Causes, Diagnosis & Compassionate Care 🐱🩸

Hi there! I’m Dr. Duncan Houston BVSc, veterinarian and founder of Ask A Vet. In this extensive 2025 guide, we cover polycythemia—a rare but serious blood condition marked by abnormally elevated red blood cell (RBC) mass. Left untreated, thickened blood can impair breathing, brain, muscle, and heart function. This article explains types, signs, diagnostics, treatment—including phlebotomy, hydroxyurea, supportive care—and lifelong monitoring strategies tailored for feline companions.

📘 1. Understanding Polycythemia

Polycythemia, also called erythrocytosis, elevates hematocrit (PCV) above normal—typically >45–50% in cats with absolute increase, or <60% in relative forms like dehydration :contentReference[oaicite:2]{index=2}.

🔍 2. Types of Polycythemia

• Relative: High PCV due to dehydration/plasma loss—cells proportionally increased :contentReference[oaicite:3]{index=3}.
• Transient: Stress-induced splenic contraction—short-term elevation :contentReference[oaicite:4]{index=4}.
• Absolute:
  • Primary (polycythemia vera): Bone marrow overproduction—PCV often >65%, normal EPO :contentReference[oaicite:5]{index=5}.
  • Secondary—appropriate: Chronic hypoxia (cardiac/respiratory disease) increases EPO :contentReference[oaicite:6]{index=6}.
  • Secondary—inappropriate: EPO-secreting tumors or renal disorders :contentReference[oaicite:7]{index=7}.

👀 3. Clinical Signs to Recognize

Signs stem from hyperviscosity and include:

• Lethargy, weakness, exercise intolerance
• Increased thirst & urination
• Gum redness, bleeding, nosebleeds
• Neurologic episodes: seizures, blindness, tremors
• Poor perfusion: ataxia, behavior changes :contentReference[oaicite:8]{index=8}.

🔬 4. Veterinary Diagnostic Approach

1. History & physical: assess dehydration, heat exposure, chronic disease.
2. Bloodwork: CBC confirms high PCV, RBC count; biochemistry screens totals proteins and organ health.
3. EPO assay: Low in primary, high in secondary :contentReference[oaicite:9]{index=9}.
4. Imaging: Radiographs, ECG, echo, or ultrasound evaluate cardiopulmonary or renal causes :contentReference[oaicite:10]{index=10}.
5. Bone marrow biopsy: Confirms myeloproliferative disease in primary forms :contentReference[oaicite:11]{index=11}.

🛠️ 5. Treatment & Management Strategies

🌡️ A. Stabilization & Relative Forms

• IV fluids to correct dehydration and dilute PCV :contentReference[oaicite:12]{index=12}.
• Optimize underlying causes: treat dehydration, heat stress.

💉 B. Phlebotomy & Myelosuppression

• Phlebotomy: remove ~7 mL/kg blood, replace with fluids to reduce PCV to ~45–50% :contentReference[oaicite:13]{index=13}.
• Hydroxyurea: suppresses RBC production; dosing ~10–15 mg/kg daily, titrated via CBC every 1‑4 weeks :contentReference[oaicite:14]{index=14}.
• Occasional phlebotomy may continue after initiating hydroxyurea :contentReference[oaicite:15]{index=15}.

🩺 C. Managing Secondary Disease

• Treat hypoxia-causing diseases (CHF, COPD, hyperthyroidism).
• Address neoplasia, renal disease, and erythropoietin-secreting tumors :contentReference[oaicite:16]{index=16}.

⚠️ D. Supportive & Preventive Care

• Avoid dehydration and stress triggers.
• Consider low-dose aspirin for thrombosis risk.
• Monitor for chemotherapy side effects: GI upset, cytopenias :contentReference[oaicite:17]{index=17}.

📆 6. Monitoring & Prognosis

• Follow-up CBC weekly → monthly → every 3 months :contentReference[oaicite:18]{index=18}.
• PCV targets: <50–55%. Signs below PCV improve; monitor proteins :contentReference[oaicite:19]{index=19}.
• Primary form: survival often >5 years; rare progression to leukemia/fibrosis (~3–19%) :contentReference[oaicite:20]{index=20}.
• Secondary forms: prognosis hinges on correctable disease course.
• Relative/transient forms: excellent outcome when underlying causes resolved.

🏡 7. Home Care & Quality‑of‑Life Support

• Keep your cat well‑hydrated, cool, and stress‑free.
• Track thirst, urination, energy, appetite using the Ask A Vet app.
• Record medications, phlebotomy dates, lab reminders via app.
• Ensure regular vet rechecks; maintain low-sodium diet if heart‑related.

📚 8. Case Studies

“Sansa,” a 2.5 yr DSH cat, admitted with PCV 80%, hind-limb weakness. Phlebotomy reduced PCV to 62%, hydroxyurea tapered over months. Follow‑up at 2 years showed full clinical resolution with ongoing monitoring :contentReference[oaicite:21]{index=21}.

“Unknown DSH” with PCV 75%, mild heart changes—treated with hydroxyurea and phlebotomy. Resolved neurologic signs, maintained control for over 2 years :contentReference[oaicite:22]{index=22}.

🚨 9. When to Seek Veterinary Attention

• Sudden lethargy, bleeding, seizures, vision loss.
• Signs of dehydration or heart strain.
• Side effects of chemo: vomiting, appetite loss.
• Post-phlebotomy monitoring: pale gums, weakness.

✨ 10. Final Takeaway

Although rare, feline polycythemia can be life-threatening—but with early recognition, precise diagnosis, and tailored treatment (phlebotomy, chemo, supportive care), many cats enjoy long-term health. At Ask A Vet, we provide tele-support, symptom tracking, medication reminders, and care planning to guide your cat every step toward wellness 🐾❤️.

For personalized follow-ups, lab scheduling templates, or tele-consultation support, visit AskAVet.com or download the Ask A Vet app. We’re with your feline friend for the long journey ahead.