Anaemia is a medical term referring to a reduced number of circulating red blood cells (RBC’s), Hemoglobin (Hb) or both. It is not a specific disease but rather results from some other disease process or condition. In Kitten Rescue and Adoption Chiang Mai, we have come across anaemia in stray cats that have recently given birth and those that have Leukemia. 

Hemoglobin delivers oxygen to the cells and tissues of the body so an anaemic cat will exhibit symptoms related to lack of oxygen. RBC’s are produced in the bone marrow and are released into the blood where they circulate for c2 months. As they age or are damaged, they are removed from the bloodstream and their components are recycled to form new RBC’s. 


Warning signs that a cat is anaemic or becoming anaemic include:

  • Pale gums
  • Acting tired, weak, or listless
  • Faster-than-normal pulse
  • Lack of appetite
  • Weight loss
  • Black, tarry stools
  • These signs can vary from pet to pet and really depend upon the underlying cause of the anemia. In some situations, your cat may present no signs at all!

What causes anaemia in cats?

Many diseases can cause a decrease in the number of red blood cells or hemoglobin. These are grouped into:

  • diseases that cause blood loss
  • diseases that cause hemolysis (red blood cell breakdown and destruction), and 
  • diseases that decrease the production of red blood cells through bone marrow suppression.

The main causes of blood loss in cats include:

  • Trauma or injury to blood vessels or internal organs resulting in bleeding
  • Severe parasitic infestations with fleas, ticks, and hookworms (particularly dangerous for kittens)
  • Tumors of the intestinal tract, kidneys, and urinary bladder
  • Diseases that prevent proper clotting of blood

The main causes of hemolysis in cats include:

  • Autoimmune disease
  • Feline leukemia virus (FeLV)
  • Blood parasites such as Hemobartonella
  • Chemicals or toxins
  • Neoplasia (cancer)

The main causes of bone marrow suppression in cats include:

  • Any severe or chronic disease (such as chronic kidney or liver disease)
  • Very poor nutrition or nutritional imbalances
  • Autoimmune disease
  • Feline leukemia virus (FeLV)
  • Feline immunodeficiency virus (FIV)
  • Chemicals or toxins
  • Neoplasia (cancer)

Iron deficiency anaemia is a common disease in people, especially women. However, this iron deficiency is rare in cats and only develops secondary to severe chronic blood loss or in cats that are on very unbalanced diets.


Diagnosis will start with a blood test. Usually several tests are performed on the blood sample but they will form part of a CBC (Complete Blood Count). The most common test to diagnose anaemia is the Hematocrit or PCV (Packed Cell Volume). To measure the PCV, a blood sample is processed in a centrifuge to spin down or separate the red blood cells from the plasma (the liquid part of the blood). After separation, the percentage of RBC’s is measured. 25% to 45% of a normal cat’s blood will be red blood cells. If the PCV is below 25% the cat is anaemic. Other tests to determine anaemia include the RBC count and the Hemoglobin count. 

Attached are two blood tests carried out on a stray cat called Snowy. She had lived rough for a year before we managed to catch her. The first blood test, carried out in February 2018, was pretty standard although her WBC (White Blood Cell) count was a little low. In May 2018 she lost her appetite, was clearly tired all the time and generally feeling depressed. A test showed that she had Leukemia. Despite medication, she continued to deteriorate so we carried out another blood test. This time her WBC count had risen but she had very severe anaemia. Her Hematocrit levels had dropped from 41% to just 9%. Our only option was a blood transfusion.



If the cat’s anaemia is so severe that it is life threatening, a blood transfusion will be needed. The main purpose of a blood transfusion is to stabilize the cat while the underlying cause of the anaemia is determined and other treatments can begin to take effect.

Further treatment will be determined once the underlying disease causing the anaemia has been diagnosed. Treatments may include corticosteroids, anthelmintics (de-worming medications), other medications, or surgery. 

The prognosis for cats with anaemia is based on the specific diagnosis and the patient’s condition prior to initiating treatment. Most cats, if the anaemia is diagnosed early and they are in relatively good health, have a good prognosis. Cats that are anaemic due to toxins, cancer or autoimmune diseases, or have suffered severe trauma have a less favorable prognosis.

All cats are at risk of anaemia in one form or another because there are so many different conditions and diseases that result in an anaemic state. For example, a cat or kitten with a parasitic infestation, such as worms or fleas, could experience blood loss and anemia — another reason why flea and tick prevention is so important!

Certain medications, such as cancer-therapy drugs and anti-inflammatory drugs, may also increase the risk of anaemia.

Blood Types

Cats will be one of three blood types: A, B and AB (rare). Most cats have type A blood – approximately 90% of domestic shorthair cats have Type A blood. This ratio varies from country to country[1]. Other cat breeds have a much higher incidence of Type B blood. There is no ‘universal donor’ blood type in cats – a very small amount of the wrong blood type can kill a cat if is sensitized to the blood. 

Blood Transfusion

The most common indications for blood transfusion in cats includes acute blood loss, coagulopathy and anaemia[4]. Multiple long-term transfusions have been reported in cats, with some cats receiving up to 15 serial transfusions and surviving[5].Testing of donor blood for blood group and FeLV and FIV status is essential[6].  As a rule of thumb, A type blood-groups must receive A-type blood, B-groups must receive B-group blood, and AB-blood group cats can receive either A or B-group blood. Suitable Feline Donors should be clinically healthy, preferably over 4kg in weight and of a suitable temperament for sedation/ restraint. Blood tests will be done to check that the donor is FeLV, FIV and M. haemofelis negative. 

50 ml (1% of body weight) of blood (standard unit) in cats is a common procedure. Collection of a standard unit of blood does not significantly change blood pressure and heart rate in healthy donor cats. The donor cat will be placed under general anaesthesia. The entire transfusion should be completed within 4 hours. The recipient cat will need to be monitored regularly for up to 8 hours after transfusion for reactions such as anaphylaxis, collapse, vomiting, urticaria, increased heart rate, temperature, or respiratory rate.

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