When to see a vet urgently
Contact a vet immediately if your cat shows any of these signs:
- difficulty breathing, even at rest;
- collapse or an inability to stay on their feet;
- almost white gums and marked weakness;
- heavy bleeding after an injury or a rapid deterioration in their condition.
You can find a vet near you.
Overview
Red blood cells and haemoglobin carry oxygen throughout the body. When their levels fall, organs and tissues suffer from a lack of oxygen, known as hypoxia. In cats, anaemia may develop suddenly, for example following blood loss, or gradually as a result of chronic disease. Depending on the cause, it is divided into several forms: anaemia due to blood loss, haemolytic anaemia (the breakdown of red blood cells), iron-deficiency anaemia and anaemia of chronic disease.
Bone marrow makes new red blood cells to replace ageing ones. Reticulocytes are young red blood cells, and their number indicates how the bone marrow is responding to anaemia. In regenerative anaemia, production increases. In non-regenerative anaemia, too few new cells are made. This distinction helps in finding the cause, but neither term on its own tells you how serious the condition is or what treatment is needed.
Causes
- Blood loss: injuries, operations, internal bleeding and parasitic infestations.
- Infections and parasites: viral diseases (FeLV, FIV), haemoplasmosis (Mycoplasma haemofelis), fleas and intestinal parasites.
- Immune disorders: autoimmune haemolytic anaemia, in which the body destroys its own red blood cells.
- Nutritional deficiencies: a lack of iron and B vitamins.
- Chronic diseases: kidney failure, tumours and inflammation.
Tiredness alone is not enough to establish iron deficiency. In cats, it is more often caused by prolonged blood loss than by too little iron in the diet. Blood-feeding parasites may be responsible in a kitten; in an older cat, investigations may include checking for bleeding in the digestive tract. Changing the diet therefore does not replace finding the cause. The vet uses the investigation results to assess whether there is evidence of a nutrient deficiency.
Risk factors
- kittens and elderly cats;
- cats that go outdoors, because of parasites and injuries;
- chronic viral infections (FeLV, FIV);
- poor nutrition or unbalanced diets;
- breeds with inherited blood abnormalities, which are rare but possible.
Symptoms
Anaemia can cause various symptoms, but the most common signs are:
- pale mucous membranes, including the gums and the lining of the eyelids;
- tiredness, sleepiness and reduced activity;
- faster breathing and heart rate;
- loss of appetite and weight loss;
- fainting or an unsteady gait in severe cases;
- a tendency to bleed and slow wound healing.
A tendency to bleed may be associated with a clotting disorder underlying the anaemia, causing blood loss. It is therefore a possible cause as well as a feature associated with anaemia.
Anaemia that develops slowly may go unnoticed at home because the body has time to adapt. Your cat may simply play less than before or withdraw to rest. With sudden anaemia, there is no comparable time to adjust. Few symptoms do not rule anaemia out, and you cannot judge a seemingly lively cat's blood values by their appearance.
Yellowish gums or whites of the eyes may be associated with red blood cells breaking down faster than usual. Black stools, meanwhile, may suggest bleeding in the digestive tract. Tell your vet about these changes: they help guide investigations, but do not establish the cause of anaemia on their own.
Possible complications
A lack of oxygen affects every organ. With prolonged anaemia, the heart, liver, kidneys and brain suffer. This can lead to heart failure, organ damage or, in cases of acute blood loss, shock and death.
Diagnosis at the vet
The vet uses several investigations to establish the cause and type of anaemia:
- a complete blood count, including red blood cells, haemoglobin and haematocrit;
- blood biochemistry tests;
- a bone marrow examination if needed;
- viral tests (FeLV, FIV);
- tests for parasites, including worms, fleas and blood parasites;
- imaging, such as ultrasound and X-rays, to identify bleeding or tumours.
Haematocrit is the proportion of a blood sample's volume made up of red blood cells. The blood count also examines white blood cells and platelets. This shows whether the abnormality is limited to red blood cells or affects other blood cells too. A blood smear allows cells to be examined under a microscope: their size, shape and any parasites can provide further clues.
The bone marrow response is not apparent immediately after sudden blood loss. An early sample may therefore suggest that new red blood cells are not being made, even though production will increase later. The vet interprets reticulocytes alongside the duration of symptoms and other findings. A repeat sample may be needed before reaching a final assessment. The result is therefore considered in the context of your cat's overall situation.
A bone marrow sample is considered particularly when there is no explanation for poor red blood cell production or when the numbers of several types of blood cell are low. It is not automatically part of the investigation for every anaemic cat. Blood and urine tests also assess organ function, while a stool sample can be used to look for blood and parasites.
A blood smear, reticulocyte count and the rest of the blood count answer different questions. Cell numbers show the extent of the shortage, young cell numbers show the production response, and microscopic examination reveals the cells' characteristics. Not all tests need to be completed at the same time. Anaemia may therefore be confirmed before its precise cause is known, with further investigations chosen according to the initial findings.
If blood loss is suspected, also mention black stools, vomiting or a recent injury, even if there is no blood on the coat. Internal bleeding can go unnoticed by an owner. The vet decides whether imaging or another investigation is needed to locate the bleeding. The absence of an external wound does not, on its own, rule out blood loss.
At the appointment, explain when the symptoms began and mention previous illnesses, medicines, supplements, travel and possible exposure to poisons. It is also useful to know whether an indoor cat could have gained access to harmful substances. This information helps the vet target investigations without examining every possible cause in the same way.
How kidney disease is linked to anaemia
The kidneys produce erythropoietin, a hormone that signals to the bone marrow that red blood cells are needed. In chronic kidney disease, this communication may weaken. Understanding kidney-related anaemia therefore requires more than counting red blood cells: kidney function must also be assessed.
A cat with kidney disease may also have weight loss, a poor appetite and increased drinking and urination. It is worth recording these observations for the appointment. They do not distinguish anaemia from kidney disease, because the problems can occur together. Urine concentration, kidney blood values and blood pressure help complete the picture.
Treatment and follow-up
Treatment targets the cause of the anaemia. Treating parasites or an infection aims to stop cells being lost or destroyed. Immune-mediated disease may require medication that suppresses the immune system. In severe anaemia, a blood transfusion supports oxygen transport while the underlying disease is treated. Before a transfusion, blood compatibility is tested to reduce the risk of reactions.
For anaemia associated with kidney disease, the vet may consider medication to support red blood cell production. Monitoring kidney disease also involves assessing fluid balance, nutrition and blood pressure. Correcting a single blood value does not cover everything a sick cat needs. Follow-up checks are tailored to the problems identified in your cat.
What to monitor at home
If your cat has been diagnosed with FeLV, monitor weight, eating, activity, litter tray visits and the appearance of the mouth and eyes. Changes in these may warrant another veterinary assessment. Written records help describe what has happened and in what order. An FeLV diagnosis alone does not tell you when a cat will become seriously ill: the course varies, and a cat may remain well for a long time.
For a cat with kidney disease, water should be easy to reach at home. Clean water bowls in several places may make drinking easier. Wet food recommended by your vet can help support fluid intake. Tell the treating vet if appetite worsens or weight falls. The stage of kidney disease and the response to treatment affect the prognosis, so other cats' experiences do not directly describe your own cat's situation.
Prevention
- regular worming and protection against external parasites;
- vaccinations to help prevent viral infections;
- a varied diet with enough vitamins and trace elements;
- monitoring chronic diseases, particularly those affecting the kidneys and liver;
- regular veterinary health checks.
Parasite control and vaccination are planned according to your cat's exposure risk. FeLV, or feline leukaemia virus, can disrupt blood cell formation. Avoiding contact with infected cats reduces the risk of catching the virus. Supervised outdoor access or a secure outdoor enclosure helps prevent encounters and fights with unfamiliar cats.
Arrange FeLV testing for a new cat before introducing them to other cats. If an infection is diagnosed in the household, the need to test the other cats is also assessed. Vaccination reduces the risk but does not provide complete protection or treat an existing infection. Preventing anaemia therefore also involves considering the cat's living environment.
This text provides general information and does not replace veterinary care. If your cat develops symptoms, contact a vet.
Frequently asked questions
Can anaemia in cats be cured?
That depends on the cause. Addressing treatable blood loss or an infection may help red blood cell numbers recover, but chronic kidney disease or bone marrow disease may require long-term monitoring. The prognosis is assessed according to the diagnosis, the severity of the anaemia and the response to treatment.
Can a cat pass anaemia to another cat?
Anaemia itself is not an infection. However, an infectious disease such as FeLV may underlie it. Based on the investigation results, the vet assesses whether cats living in the same home need tests or changes to their living arrangements.
Is iron-rich food enough to treat anaemia?
Not without finding the cause. Iron deficiency is only one possible explanation, and it too may result from continuing blood loss. The treatment plan is based on investigations, so the need for an iron supplement is decided by the vet.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Anaemia, Cornell Feline Health Centre, accessed 2026-11-02.
- Anaemia in Cats, Merck Veterinary Manual, accessed 2026-11-02.
- Chronic Kidney Disease, Cornell Feline Health Centre, accessed 2026-11-02.
- Feline Leukaemia Virus, Cornell Feline Health Centre, accessed 2026-11-02.
- Overview of Anaemia in Animals, Merck Veterinary Manual, accessed 2026-11-02.