Pet Factsheets


Anaemia means a shortage of red blood cells in the circulation. Anaemia is not a disease but it is a sign that there may be something seriously wrong in the body. There are many different causes of anaemia in cats and in most cases your vet will need to perform a variety of tests to work out what is wrong. Severe anaemia can be life-threatening and requires urgent treatment.

What are red blood cells?

Red blood cells are important cells that carry oxygen around the body. Red blood cells are mainly made in the bone marrow but also, in the liver and spleen. Their red colour comes from a pigment called haemoglobin. The red blood cells pick up oxygen whilst travelling through the lungs and transport this to the body tissues, where it is exchanged for the waste gas carbon dioxide. The red blood cells transport the carbon dioxide back to the lungs where it is removed from the body in exhaled breath.

Red blood cells are active for around 70 days, after which they are removed from the circulation. Continuous production by the bone marrow ensures that the total numbers remain the same.

How do I know if my cat is anaemic?

In the early stages, there may be few symptoms of anaemia. If the anaemia develops slowly it can become quite severe without the animal showing signs because the body has time to get used to the lower oxygen levels. The first sign of anaemia may be low energy levels and general weakness due to reduced oxygen supply to the muscles. Anaemic animals often have a poor appetite. If you lift your cats lips you may notice that its gums are pale or even white, although do not be alarmed when you check your cat as gums in normal cats often look quite pale.

How will my vet know if my cat has anaemia?

Your vet will need to examine your cat closely to identify the signs of anaemia. Depending on what is causing the anaemia, there may also be other changes such as jaundice (yellowing of the skin and membranes of the eyes, nose and mouth). A diagnosis of anaemia can usually be made on a single blood test, however your vet may need to perform a number of tests to find out what is causing the anaemia. It is important to establish the cause of anaemia in order to treat the underlying condition.

Common tests that may be required include:

  • Blood tests these allow your vet to tell how severe the anaemia is, and also in some cases indicate what has caused it. A large number and variety of tests may be required; tests are often repeated frequently to assess progress and response to treatment.
  • X-rays and ultrasound scans these may be used to look for internal problems causing the anaemia, eg blood loss into the abdomen or chest, or perhaps cancers.
  • Biopsies samples may be taken from any lumps, and of the bone marrow, to assess its function and to look for abnormalities.

Why is my cat anaemic?

Anaemia can develop in a number of ways.

Blood loss

The most obvious cause is from blood loss, eg after an accident. First aid in accident and emergency situations is designed to limit blood loss as much as possible. Heavy flea burdens in kittens can also cause potentially fatal anaemia.

Haemorrhage can also occur much more slowly if small amounts of blood are lost from the body over a prolonged period of time. This type of bleeding is often associated with cancers bleeding within the body. If blood loss is occurring slowly, particularly if bleeding is into the urine or faeces, it is sometimes not noticed until signs of anaemia develop. In these cases the anaemia may be quite severe before signs are noticed because the body has time to get used to the lower oxygen levels.

Other causes of anaemia

There are many other causes of anaemia that are seen regularly in cats. In normal animals red cell production is increased if the animal becomes anaemic. However, if there is a problem with red blood cell production or the red blood cells are destroyed in larger numbers than normal then anaemia may develop.

One cause of anaemia in cats is infection with a parasite that lives in or on red blood cells (feline infectious anaemia caused by Haemoplasma infection, egMycoplasma haemofelis). When the body defences recognise the parasite and try to destroy it they actually damage red blood cells which are then removed from the blood. If the bone marrow cannot produce red blood cells at the same rate as they are being lost then replacement of old cells does not occur and anaemia eventually develops. Anaemia is also common in cats with chronic illnesses, particularly kidney failure.

One of the challenges for the veterinary surgeon is to determine exactly why the anaemia is occurring, and how the body is responding. It is important to investigate all anaemias so that the correct treatment can be worked out.

Can my cat be treated for anaemia?

Effective treatment depends on the diagnosis of the underlying problem. Surgical or medical options may be available depending on the cause. If the immune system is destroying red blood cells within the body then drugs can be given to modify the actions of the immune system. Certain blood parasites may cause anaemia and these can be treated with appropriate medication, eg Haemoplasma infections are treated with certain antibiotics. Kidney disease can be managed in the long term but the anaemia it causes can be difficult to control.


If your cat has anaemia it is very important that your vet works out what is causing it so that the best treatment can be started as soon as possible. Anaemia often indicates a serious underlying problem which must be treated. Without treatment the underlying disease and the anaemia may get worse and this will make your cat feel more unwell.