Polycythaemia in Dogs and Cats: When Too Many Red Blood Cells Is a Problem

What is polycythaemia in dogs and cats?

Polycythaemia (also called erythrocytosis) is a condition in which a dog or cat has an abnormally high number of red blood cells circulating in the bloodstream. This thickens the blood, impairs oxygen delivery to tissues, and can cause serious neurological, cardiovascular, and organ complications if left untreated. MaxPetz in Delhi provides veterinary diagnostics and blood disorder management for pets showing signs of this condition.

Polycythaemia is classified into three types:

• Relative polycythaemia: Caused by dehydration — the red blood cell count appears elevated because plasma volume is reduced. This is the most common and often reversible form.
• Secondary polycythaemia: The body produces excess red blood cells in response to low oxygen levels (hypoxia) or, less commonly, abnormal hormone signalling.
• Primary polycythaemia (Polycythaemia Vera): A rare bone marrow disorder in which red blood cells are overproduced independent of oxygen levels. This is the most serious form.

What causes too many red blood cells in a dog or cat?

The root cause of polycythaemia depends on its type. Identifying the underlying cause is essential before any treatment can be planned.

What are the symptoms of high red blood cell count in dogs and cats?

Clinical signs of polycythaemia arise because thickened blood moves slowly, reducing oxygen delivery and increasing the risk of clotting. Symptoms can be subtle at first and worsen progressively.

Common signs in dogs:

• Reddened or brick-red mucous membranes (gums, conjunctiva)
• Lethargy and exercise intolerance
• Increased thirst and urination (polydipsia/polyuria)
• Nosebleeds or bleeding from mucous membranes
• Seizures or disorientation (in advanced cases)
• Distended, engorged blood vessels visible in the eyes
• Weakness or stumbling gait

Common signs in cats:

• Bright red or dark-red gums
• Behavioural changes — confusion, circling, or head pressing
• Vomiting
• Blindness (due to retinal haemorrhage from high blood viscosity)
• Increased thirst and urination
• Generalised weakness

How is polycythaemia diagnosed in pets?

Accurate diagnosis requires a combination of blood tests, imaging, and sometimes bone marrow evaluation. A single elevated haematocrit reading is not sufficient to confirm polycythaemia — the type must be established before treatment begins.

The diagnostic process at a veterinary haematology centre typically includes:

1. Complete Blood Count (CBC): Measures haematocrit (PCV), haemoglobin, and red blood cell indices. A PCV above 65% in dogs or 55% in cats is generally considered elevated.
2. Serum biochemistry panel: Assesses kidney and liver function, and rules out dehydration as the cause.
3. Arterial blood gas analysis: Determines blood oxygen levels to differentiate secondary (hypoxic) from primary polycythaemia.
4. Erythropoietin (EPO) levels: Low EPO suggests primary polycythaemia vera; elevated EPO points to a secondary cause.
5. Abdominal ultrasound: Screens for kidney masses or other tumours that may be secreting EPO.
6. Chest radiographs: Evaluates for cardiopulmonary disease contributing to hypoxia.
7. Bone marrow biopsy: Reserved for cases where primary polycythaemia vera is suspected.

Explore pet blood disorder diagnostics and veterinary diagnostic procedures available at MaxPetz Delhi.

What is the treatment for polycythaemia in dogs and cats?

Treatment depends entirely on the type and underlying cause of polycythaemia. Managing the root condition is as important as reducing the red blood cell count.

Relative polycythaemia:

• Intravenous fluid therapy to correct dehydration
• Treatment of the underlying cause (e.g., vomiting, diarrhoea)
• Usually resolves fully once hydration is restored

Secondary polycythaemia:

• Treat the primary disease (heart disease, lung disease, kidney tumour)
• Phlebotomy (controlled removal of blood) may be used to provide immediate relief of symptoms while the underlying condition is managed
• Resolution timeline varies — secondary polycythaemia linked to a treatable cause can improve over weeks to months once the cause is addressed

Primary polycythaemia vera:

• Periodic phlebotomy to reduce blood viscosity and relieve symptoms
• Hydroxyurea (a cytoreductive medication) to suppress bone marrow overproduction — used under close veterinary supervision
• Regular CBC monitoring to guide dosing adjustments
• This form is managed long-term rather than cured; with consistent treatment, affected pets can maintain a reasonable quality of life

When should you bring your pet to a vet for polycythaemia?

Seek veterinary assessment promptly if your dog or cat shows any of the following signs — do not wait more than 24 hours if multiple symptoms are present simultaneously:

• Gums that appear persistently red, brick-red, or dark rather than pink
• Unexplained nosebleeds or bleeding from the eyes or mouth
• Sudden behavioural changes — confusion, circling, or pressing the head against walls
• A seizure episode, even if the pet appears to recover quickly
• Sudden loss of vision or apparent blindness
• Lethargy lasting more than 48 hours combined with reduced appetite
• Increased thirst and urination that has developed over days to weeks without an obvious cause

If your pet has already been diagnosed with a heart condition, chronic lung disease, or kidney disease and you notice any of the above signs, contact your vet the same day — these conditions increase the risk of secondary polycythaemia.

How does MaxPetz Delhi support pets with blood disorders?

MaxPetz in Delhi offers veterinary care for pets with blood disorders including polycythaemia, combining diagnostic precision with compassionate clinical management. The team uses cutting-edge technology to carry out the haematological workup — from complete blood counts and biochemistry panels to imaging — needed to classify polycythaemia accurately and guide the right treatment pathway for each individual pet.

For pets requiring ongoing management of primary polycythaemia vera, MaxPetz Delhi provides structured follow-up protocols including periodic CBC monitoring and medication review, so that treatment remains appropriate as the condition evolves.