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Anaemia in Cats

Eyes of a cat with anaemia

Anaemia in cats occurs when red blood cell numbers or haemoglobin levels fall low enough to reduce oxygen delivery. We measure its severity using the packed cell volume (PCV). PCV measures the proportion of blood that is made up of red blood cells.

In cats, PCV doesn’t always reflect how sick they are or how well they might do. Even with very low PCV, many recover if the cause is identified and managed.

Anaemia in cats is rarely simple. It often develops alongside other diseases, and the signs are easy to miss. Identifying whether it is regenerative or non-regenerative, and interpreting test results in the context of the cat’s condition, is critical to finding the cause and treating it effectively.

Recognising anaemia in cats

The clinical signs of anaemia vary with the severity of the condition and the speed at which it develops. In mild or gradual cases, cats may become less active, eat less and spend more time resting. Mucous membranes may appear pale, and examination may reveal a faster heart rate with weak or thready pulses. Some cats withdraw or interact less than usual.

When anaemia is severe or develops suddenly, the signs are more pronounced. Cats may collapse or appear severely weak. Bradycardia or tachycardia, exaggerated pulse quality, poor peripheral circulation and a drop in body temperature can also occur when oxygen delivery is critically impaired.

Cats can tolerate a very low PCV if the anaemia progresses slowly, and may appear more stable than expected given their test results.

 

A practical approach to classifying anaemia in cats

STEP 1 – Regenerative vs non-regenerative

The first question to answer is whether the anaemia is regenerative or not. This will help decide which causes are most likely and what to test for next. To work this out, you need to complete a full blood count, a reticulocyte count and review a smear.

If the anaemia is regenerative, it means the bone marrow is producing new red cells. In cats, this usually takes two or three days to show in the blood. In older cats it can take longer because the marrow responds more slowly.

Sometimes anaemia appears non-regenerative simply because it is too early to see a response. This is called a pre-regenerative anaemia. Chronic diseases can also blunt or prevent regeneration altogether, and some elderly patients may take longer to show a regenerative response compared to young cats.

Step 2 – Broad categories

Once you know whether the anaemia is regenerative or not, the next step is to consider how the anaemia may have developed, e.g. the aetiology of anaemia. This approach helps organise your differentials and guides which tests to run.

The first category is blood loss, either acute or chronic. Acute loss is usually obvious and can result from trauma, surgery or a bleeding lesion. Chronic blood loss is more subtle and can come from a gastrointestinal ulcer, parasites or other low-grade sources that may not be immediately apparent.

The second category is increased destruction of red blood cells (haemolysis). In cats, this can be immune-mediated, caused by haemoplasma species infection or other infectious disease, or the result of oxidative damage such as Heinz body formation (e.g. due to drugs, onion toxicity, etc). Cats are more prone to oxidative damage than dogs because of the structure of their red blood cells.

The third category is reduced production of red blood cells. This occurs when the bone marrow cannot respond appropriately. It can be due to primary bone marrow disease, chronic inflammatory or neoplastic conditions, or nutritional deficiencies.

Diagnostic workup for anaemic cats

Physical examination

The diagnostic process begins with a thorough examination. Check mucous membrane colour for pallor and assess pulse quality, heart rate and temperature. Look for any evidence of external or internal bleeding, and note signs of cardiovascular instability such as weak or hyperdynamic pulses. Be sure to examine inside the mouth for bleeding ulcers of the hard palate (Menrath ulcer).

Laboratory testing

A complete blood count, reticulocyte count and packed cell volume with total protein provide the foundation for assessing anaemia. Smear examination gives additional detail on red cell morphology and platelet numbers, and helps verify automated results. Biochemistry can identify underlying disease processes and may reveal mild bilirubin elevation in haemolytic cases.

Platelet counts from analysers are often inaccurate in cats, so smear confirmation is important. A saline agglutination test distinguishes pathological agglutination from rouleaux, which is a normal finding in cats.

Advanced diagnostics

PCR testing can identify infectious causes such as haemoplasmas or retroviruses. Imaging, including radiographs and ultrasound, is useful for detecting neoplasia, internal haemorrhage or organ changes, but note that it can be difficult to find bleeding lesions that are small.

For non-regenerative or refractory anaemia, a bone marrow aspirate or biopsy may be necessary to assess marrow function and rule out serious underlying disease.

Common causes of anaemia in cats

In young cats

In young cats, trauma is a frequent cause of acute blood loss, especially in outdoor animals. Rodenticide toxicity can also lead to significant bleeding, although it is less common in cats than in dogs.

Haemoplasma infections are another important consideration, particularly in young, male, outdoor cats. These infections can cause a marked haemolytic anaemia and are usually confirmed with PCR testing.

Feline infectious peritonitis (FIP) is another cause seen in younger cats, often associated with a mild to moderate non-regenerative or haemolytic anaemia. Primary immune-mediated haemolytic anaemia (IMHA) also tends to occur in this age group. Unlike secondary IMHA, which is triggered by another disease, primary IMHA is more likely to appear in otherwise healthy young cats. Feline leukaemia virus infection can also result in anaemia, often in younger cats.

In older cats

In older cats, we often find that anaemia is linked to chronic kidney disease. Reduced erythropoietin production and other effects of kidney dysfunction can lead to a mild to moderate, non-regenerative anaemia that develops gradually.

Neoplasia is another common cause in this age group. Both lymphoma and leukemia can suppress bone marrow function or increase the destruction of red blood cells, depending on the type and stage of the disease.

Bone marrow disorders, such as fibrosis, myelophthisis or infiltrative diseases, can also impair red cell production. In some cases, the anaemia is part of a broader syndrome of marrow failure affecting multiple cell lines.

Anaemia of chronic disease or chronic inflammation is also frequently seen. This form is usually mild and non-regenerative, and often accompanies conditions like inflammatory bowel disease, liver disease or low-grade infections.

Treatment and management for anaemic cats

Appropriate management of feline anaemia depends on identifying and addressing the cause. Whether the anaemia is due to trauma, infection, neoplasia or an immune-mediated process, treating the underlying disease is key to improving outcomes.

Supportive care can play an important role, particularly in severe cases. Blood transfusions are necessary on occasion; however, this decision should be based on how the cat is coping clinically with their anaemia (transfusion triggers) rather than a single PCV result alone.

Cats with chronic kidney disease may benefit from erythropoietin analogues, such as darbepoetin, which can help stimulate red blood cell production when the kidneys can no longer produce enough on their own.

Vitamin B12 is safe and commonly used, especially in cats with gastrointestinal disease or poor absorption. Iron may be considered in cases of chronic blood loss, but not all cats with anaemia need it.

It’s also important to consider the use of antinausea medications and analgesia where required.

Prognosis and clinical summary

Anaemia in cats is complex but manageable with a clear, systematic approach. Paying close attention to clinical presentation, classifying the anaemia accurately and investigating the underlying cause without relying on numbers alone gives these cats the best chance of recovery.

Dr Rachel Korman recently joined The Vet Vault podcast to discuss feline anaemia. You can listen here.

Are you worried about your cat’s health?

If you are concerned about your cat, please reach out to our friendly team. Call us on 1300 228 377 or fill out the contact form below. In an emergency, please contact your local vet.

For vets – to refer a patient or book a telehealth consultation, please call us on 1300 228 377, book through the portal or fill in the form.

What are the most common signs of anaemia in cats?

Cats may seem more lethargic, eat less, rest more and appear pale. In severe cases, they may collapse, become very weak or show changes in heart rate, pulses or body temperature.

Does a very low PCV mean a cat has a poor prognosis?

Not necessarily. Many cats, especially if the anaemia developed slowly, tolerate low PCV well and can recover when the underlying cause is treated.

How is anaemia diagnosed in cats?

Diagnosis involves a full physical examination, blood tests including CBC, reticulocyte count and PCV, smear evaluation, and sometimes more advanced tests like PCR, imaging or bone marrow biopsy.

What causes anaemia in older cats?

Chronic kidney disease, neoplasia (like lymphoma or leukemia), bone marrow disorders and chronic inflammatory diseases are the most common causes in older cats.

When is a transfusion needed for a cat with anaemia?

A transfusion is based on how the cat is coping rather than the PCV alone. Some cats with very low PCV remain stable without immediate transfusion, while others with higher PCV may still require support.

Patient Stories

Our commitment to feline health is best seen in the stories of the cats we’ve had the privilege of treating. These journeys highlight the dedication, expertise and compassion that drive us.

Each patient faced unique challenges, and it was our honour to offer high-quality care and help them regain strength and happiness. We value the deep bonds with cats and their owners, knowing the difference we make in their lives.

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At 5 months old, Tango was diagnosed with Feline Infectious Peritonitis (FIP). Once considered a fatal disease, the introduction of new treatments has significantly boosted the survival rate.

Contacting Us

Pet Owners
If you would like to talk about treatment for your cat, call us on 1300 228 377 or fill in the form.
In an emergency, please contact your local vet.

Vets and Nurses
To refer a patient or book a telehealth consultation please call us on 1300 228 377, book through the portal or fill in the form. For advice calls, please see the guidelines here.

1300 228 377
1-15 Lexington Rd,
Underwood, QLD, AU, 4119
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