Early Detection

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Pet Place has an overview of anaemia in cats.

Approach to feline anaemia cases (2016) Tasker S Presentation to ANZCVS Science Week has a good overview of anaemia.

Vitamin B Deficiencies

Use of ACE Inhibitors or ARBs

Iron deficiency anaemia (2012) Naigamwalla DZ, Webb JA & Giger U The Canadian Veterinary Journal 53(3) pp250-256 has some information about iron deficiency anaemia, though it is rather technical.

Feline anaemias: a diagnostic challenge (2002) Giger U Presentation to the World Small Animal Veterinary Association World Congress explains more about how diagnosing anaemia can sometimes be a challenge.

Basic approach to anaemia diagnosis (2005) Tvedten H Presentation to the World Small Animal Veterinary Association World Congress discusses the various causes of anaemia

Feline non-regenerative anemia: pathophysiology and etiologies (2009) White C & Reine N Compendium: Continuing Education for Veterinarians 31(7) ppE1-E7 has an overview of the various causes of non-regenerative anaemia.

Anemia in animals (2019) Marks SL & Kendall A Merck Veterinary Manual discusses anaemia in a quite technical but useful manner.

Inflammation or Infection

Inflammation is a common cause of anaemia, particularly in cats with chronic diseases such as cancer or inflammatory bowel disease (IBD).

Infection may also cause non-regenerative anaemia, partly because of associated inflammation and partly because of how the body deals with bacterial infections. Bacteria thrive on iron, so if a cat has an infection, the cat's body will sequester iron (i.e. iron is stored within the body rather than released into the bloodstream). Since iron is necessary for blood cell production, iron deficiency anaemia may result. Iron metabolism in pathogenic bacteria (2000) Ratledge C & Dover LG Annual Review of Microbiology 54 pp881-941 explains more about this.

Inflammation or infection may also be seen in CKD cats, of course. Iron status of cats with chronic kidney disease (2015) Gest J, Langston C & Eatroff A Journal of Veterinary Internal Medicine 29 pp1489-1493 states "Of an interesting note, TIBC [total iron binding capacity] is decreased in inflammation. With TIBC significantly lower in cats with CKD compared to healthy cats, this study’s results support the presence of inflammation in this group of CKD cats."

If inflammation or infection is the only reason your cat has anaemia and you are able to get the cause under control, the anaemia may improve or even be fully resolved. One of my cats (who did not have CKD) was prone to pyelonephritis (kidney infections) and every time he developed pyelonephritis, he became anaemic. Once the infection was successfully treated with antibiotics, his anaemia would resolve with no other treatment.

Anemia of inflammation or chronic disease National Institute of Diabetes and Digestive and Kidney Diseases is an article about these problems in humans.

Gastrointestinal Bleeding

As stated above, gastrointestinal bleeding may be caused by uraemic toxins and may contribute to the development of non-regenerative anaemia.

Gastrointestinal bleeding may also happen for other reasons, which may mean the anaemia is regenerative, at least initially. Cornell University College of Veterinary Medicine says "Chronic external blood loss, particularly when slow or intermittent, results in a slowly developing anemia, which at first is regenerative (increased reticulocyte count). If blood loss continues long enough that body iron stores are depleted and absorption of dietary iron is inadequate to meet the demand created by increased red blood cell production, then iron becomes a limiting factor and effective erythropoiesis is decreased."

Acute gastrointestinal bleeding tends to cause anaemia to develop quickly, whereas most cats with anaemia caused by a lack of erythropoietin become anaemic gradually. Therefore if your cat's PCV level (a measure of anaemia) falls suddenly, ensure your vet considers gastrointestinal bleeding as a possible cause.

Non CKD-Related Causes of Regenerative Anaemias

In the case of regenerative anaemia, new red blood cells are being regenerated as normal in the bone marrow but for some reason they are being lost or destroyed more quickly than they should. There are several types of regenerative anaemia, and they are sometimes divided into the following classes:

• haemorrhagic: the red blood cells are being lost through blood loss

• haemolytic: the red blood cells in the bloodstream are being destroyed

Apart from the tests for anaemia mentioned below, a total protein test may help your vet decide which type of regenerative anaemia is more likely, because total protein tends to fall if there is blood loss present.

Fleas

A severe flea infestation may cause blood loss anaemia, especially in kittens, because fleas drink blood. Mar Vista Vet has more information about this.

Fleas may also cause feline infectious anaemia.

Gastrointestinal Bleeding

The blood loss resulting from gastrointestinal bleeding may cause regenerative anaemia, though if it continues for a long time, it may eventually become non-regenerative. Cornell University College of Veterinary Medicine says "Chronic external blood loss, particularly when slow or intermittent, results in a slowly developing anemia, which at first is regenerative (increased reticulocyte count). If blood loss continues long enough that body iron stores are depleted and absorption of dietary iron is inadequate to meet the demand created by increased red blood cell production, then iron becomes a limiting factor and effective erythropoiesis is decreased."

As mentioned above, gastrointestinal bleeding in CKD cats may be caused by uraemic toxins.

Acute gastrointestinal bleeding tends to cause anaemia to develop quickly, whereas most cats with anaemia caused by a lack of erythropoietin become anaemic gradually. Therefore if your cat's PCV level (a measure of anaemia; see below) falls suddenly, ensure your vet considers gastrointestinal bleeding as a possible cause.

Iron Deficiency Anaemia

Red blood cells contain a protein called haemoglobin, which transports oxygen around the body. Haemoglobin needs iron for its production. Therefore a cat with low iron levels will struggle to create new red blood cells and can develop a type of anaemia known as iron-deficiency anaemia.

This form of anaemia can be either regenerative or non-regenerative. Cornell University College of Veterinary Medicine says "iron deficiency in adult animals usually is caused by chronic blood loss." It goes on to say that "If blood loss continues long enough that body iron stores are depleted and absorption of dietary iron is inadequate to meet the demand created by increased red blood cell production, then iron becomes a limiting factor and effective erythropoiesis is decreased."

If the cat has concurrent diseases contributing to the anaemia, such as infections that cause the body to sequester (hide) iron, it is more likely that the iron deficiency anaemia will be non-regenerative.

Iron deficiency anaemia (2012) Naigamwalla DZ, Webb JA & Giger U The Canadian Veterinary Journal 53(3) pp250-256 has some information about iron deficiency anaemia, though it is rather technical.

Medication-Related Anaemia

Methimazole for Hyperthyroidism

Cats with hyperthyroidism who are being treated with methimazole may sometimes develop anaemia, though this is rare. If it is going to occur, it usually does so within the first three months of use. Stopping the medication usually resolves the problem within a couple of weeks.

Can methimazole cause anemia in hyperthyroid cats? (2013) Peterson ME explains more about this problem.

Aluminium Hydroxide Toxicity

If you are using aluminium hydroxide as a phosphorus binder, in rare cases aluminium  toxicity may occur and this may cause anaemia. Anaemia of renal disease: what is it, what to do and what's new (2011) Chalhoub S, Langston C & Eatroff A Journal of Feline Medicine and Surgery 13(9) pp629-40 states "Aluminum toxicity, from aluminum containing phosphate binders, can interfere with iron metabolism, leading to a microcytic anemia that is not responsive to iron administration"

One possible early sign of aluminium toxicity is a change in MCV. This is a measure of red blood cell size. If your cat has a low MCV (known as microcytosis), this means the red blood cells are smaller than usual. Although this may simply indicate iron deficiency, it may also be a sign of aluminium toxicity. This sign normally appears before you see physical symptoms, so be sure to monitor your cat's MCV levels if you are using aluminium hydroxide.

Cefovecin (Convenia)

Cefovecin is an injectable antibiotic in the cephalosporin class which is approved in the USA under the name of Convenia for the treatment of skin infections in dogs and cats and urinary tract infections in dogs. In Europe it is approved both for these conditions and also for the treatment of urinary tract infections in cats.

In rare cases antibiotics in this class, including cefovecin, may cause haemolytic anemia.

Oxidative Damage: Onions or Garlic

Feeding onions or garlic to cats causes a specific type of haemolytic anaemia called Heinz body anaemia.

Feline Infectious Anaemia (FIA): Mycoplasma Haemofelis

The most common cause of anaemia in otherwise healthy cats is feline infectious anaemia. This is caused by an bacterial parasite called haemoplasma, one type of which is mycoplasma haemofelis (previously known as feline haemobartonella felis). This attaches itself to the cat's red blood cells, and the cat's immune system tries to destroy it, but in the process it also destroys the red blood cells. If the cat's body cannot create new red blood cells quickly enough, the cat will develop haemolytic anaemia.

This condition is transmitted by cat bites or parasites (usually fleas), but unfortunately it does not always show up in tests because it is not continuously present. Newer PCR tests are more reliable at detecting the infective agent  but you may need to wait for the results.

Since FIA can make cats very ill, some vets treat for it even if the tests are negative or delayed. The usual treatment is an antibiotic called doxycycline, which is given for at least 3-4 weeks (sometimes six). Occasionally corticosteroids are also necessary. If the cat is severely anaemic, a blood transfusion may be required.

Pet Place has some information about FIA.

Mar Vista Vet has some good, detailed information on FIA.

Haemoplasmosis in cats: European guidelines from the ABCD on prevention and management (2018) Tasker S, Hofmann-Lehmann R, Belák S, Frymus T, Addie DD, Pennisi MG, Boucraut-Baralon C, Egberink H, Hartmann K, Hosie MJ,  Lloret A, Marsilio F, Radford AD, Thiry E, Truyen U & Möstl K Journal of Feline Medicine and Surgery 20(3) pp256-261 offers guidelines on prevention and management from the European Advisory Board on Cat Diseases.

Immune-Mediated Haemolytic Anaemia (IMHA)

Immune-mediated haemolytic anaemia is caused by an autoimmune reaction which leads the cat's body to kill off its red blood cells. This can cause severe anaemia which can be difficult to treat. The usual causes in cats are myoplasma haemofelis infection (see above) and feline leukaemia.

Possible treatments include corticosteroids and cyclosporine, though blood transfusions are also often necessary, preferably of packed red blood cells rather than whole blood.

Expert round table on immune haemolytic anaemia IMHA (2024) Laboklin Laboratory has an overview of IMHA.

Immune mediated hemolytic anemia: can we beat this disease? (2011) Mineo H Veterinary Medicine explains more about treatment options.

Veterinary Partner has an overview of IMHA.

IHMA: diagnosing and treating a complex disease (2008) Shaw N & Harrell K Veterinary Medicine discusses IMHA.

Diagnosis of immune-mediated hemolytic anemia (2013) Archer T & Mackin A Today's Veterinary Practice Jul/Aug pp32-36 discusses the diagnosis of IMHA.

Management of immune-mediated hemolytic anemia: a common hematologic disorder in dogs and cats (2014) Archer T & Mackin A Today's Veterinary Practice Mar/Apr pp41-46 discusses the treatment of IMHA.

Feline non-regenerative immune-mediated anaemia: features and outcome in 15 cases (2016) Black V, Adamantos S, Barfield D & Tasker S Journal of Feline Medicine and Surgery 18(8) pp597-602 discusses which treatments were found to be the most effective and states that treatment often needs to be provided for at least six weeks before an improvement is noted.

Hypophosphataemia (Low Phosphorus Levels)

Hypophosphataemia (low phosphorus levels in the blood may cause haemolytic anaemia, according to Immune mediated hemolytic anemia: can we beat this disease? (2011) Mineo H Veterinary Medicine.

Hemolytic Anemia (2019) Marks SL & Kendall A Merck Veterinary Manual says that this is usually "secondary to diabetes, hepatic lipidosis and refeeding syndrome."

Low phosphorus levels are very rare in CKD cat, who tend to have elevated phosphorus levels.

Breathlessness

Because of the shortage of red blood cells, which carry oxygen around the body, there is less oxygen in the body's tissues. Therefore the cat breathes more often and more deeply in an attempt to take in more oxygen.

Weakness

This is also caused by the lack of oxygen in the tissues, which means the cells cannot work as effectively.

Eating Litter or Licking Concrete

Heart Problems, Including Faster Heart Rate

Heart problems are relatively common in anaemic patients. In an anaemic cat, the heart rate increases in an attempt to push the reduced amount of haemoglobin around the body. This faster heart rate is called tachycardia. Occasionally anaemia may cause a heart murmur.

Hypertension, left ventricular hypertrophy and chronic kidney disease (2011) Taddei S, Nami R, Bruno RM, Quatrini I & Nuti R Heart Failure Reviews 16(6) pp615-20 says of human patients "Left ventricular hypertrophy (LVH) is a cardiovascular complication highly prevalent in patients with chronic kidney disease (CKD) and end-stage renal disease... In particular, the correction of anemia with erythropoietin in CKD patients is advantageous, since it determines LVH reduction."

Hypertension (High Blood Pressure)

The heart tries to provide more blood, and thus oxygen, to the body's cells by increasing the pressure with which it pumps. Increased pressure in the arteries is called hypertension, and it can lead to blindness or strokes, so it is important to treat it if present.

Oedema and Heart Failure

The heart can only compensate for the lack of haemoglobin to a certain extent. Eventually, if the problem remains untreated, blood will not circulate properly and will build up, and fluid will leak into body tissues. This causes swelling known as oedema. If oedema occurs in the lungs, it is known as pulmonary oedema, and if it is left untreated this can kill the cat.

Other Symptoms

Almost all anaemic cats experience:

• loss of appetite, often severe

• extreme lethargy

• pale eyelids or gums

• feeling cold, so they often seek out warm places.

It can be difficult ascertaining the exact cause of anaemia, and to complicate matters, more than one cause may be present.

Your vet will initially determine whether your cat is anaemic by looking at red blood cells (RBC) and packed cell volume (PCV) or haematocrit (HCT), but may also need to do further tests (reticulocytes and measures of iron) in order to ascertain the cause.

Cornell University College of Veterinary Medicine has a diagnostic algorithm for anaemia generally.

Cornell University College of Veterinary Medicine has a diagnostic algorithm for non-regenerative anaemia in particular.

Anemia diagnostic tree (2010) Kiss CM & Pierce BJ NAVC Clinician's Brief also has a diagnostic tree helping you to distinguish between both.

Feline nonregenerative anemia: diagnosis and treatment (2009) White C & Reine N Compendium: Continuing Education for Veterinarians 31(7) ppE8-12 discusses the diagnosis and treatment of non-regenerative anaemia.

Taking Blood For Testing

Your vet needs to take blood from your cat in order to run tests for CKD and anaemia. This is potentially problematic for CKD cats because, according to Managing anemia in patients with chronic kidney disease (2011) Chalhoub S, Langston CE Veterinary Medicine May 2011, "The frequent blood sampling of hospitalized patients, especially small pets, can contribute to anemia." Hospital-acquired anemia in critically ill dogs and cats: a multi-institutional study (2016) Lynch AM, Respess M, Boll AE, Bozych M. McMichael M, Fletcher DJ, De Laforcade AM & Rozanski EA Journal of Veterinary Internal Medicine 30 pp141-146 looked at patients admitted to the intensive care units of three US veterinary teaching hospitals. It found that the average PCV of feline patients was 31% upon admission, but only 26% upon discharge, and that it was more likely to have reduced if the cat had experienced more blood draws.

This can also be true for cats who are not hospitalised but who are having blood tested every few days.

If your vet wishes to test only for anaemia, it is not usually necessary to draw a lot of blood — a tiny drop taken from the ear may be sufficient (make sure the ear is warm), so ask your vet if this method could be used, though some machines do need more blood than this, especially if the clinic uses computerised analysis. Mar Vista Vet has a video showing how to take blood from the ear in diabetic cats. Dr Wendy Blount has detailed photographs showing how to do it.

Home Blood Testing

A few members of Tanya's CKD Support Group have been using a home haematocrit tester to measure PCV at home in order to spare their cats the stress of vet visits and themselves the cost of frequent tests. Of course if you are using an erythropoiesis stimulating agent (ESA) for your anaemic cat, you cannot avoid vet visits completely because you need to monitor blood pressure in cats using an ESA (though some people are now doing that at home too, see Hypertension). Personally, if I was dealing with severe anaemia (PCV below 18%), particularly if my cat was on an ESA such as darbepoetin or epoetin (Aranesp or Epogen), I think I would prefer regular vet visits. But for a stable anaemic cat, especially one who does not do well at the vet's, a home tester might be worth considering.

InSight HCT Meter is made by Woodley Veterinary Diagnostics. It is available from Praxisdienst in Germany for €159.29, US$167.10 or £132.05, plus taxes and shipping. Shipping information is here. You will also need test strips and capillary tubes. A couple of members of Tanya's CKD Support Group have bought this so far, and have found it pretty accurate, though one member felt it gave quite different readings to her vet's machine.

If you do buy a home tester, I would recommend checking your first few readings against readings at the vet's, to make sure you are doing it properly and to reassure your vet that you are obtaining accurate readings at home.

There are two types of anaemia, regenerative and non-regenerative:

Red blood cells make up most of the blood cells in the body. They are produced in the bone marrow and their rôle is to carry oxygen around the body.

Proteins on red blood cells determine the cat's blood group, which is important to know for cats who require blood transfusions (see below). 

A low red blood cell count is usually indicative of anaemia, because if a cat cannot manufacture sufficient red blood cells or if the red blood cells are being destroyed faster than the cat can make them, s/he will become anaemic.

Cats can be prone to developing anaemia because, as International Cat Care explains, "their RBCs have a shorter lifespan (around 70 days) than many other animals (around 110-120 days in dogs and humans) - this means they have a higher turnover of RBCs and anaemia can therefore develop quite rapidly if anything interferes with this."

It is even worse for CKD cats. The lifespan of red blood cells in patients with kidney disease is approximately half that of healthy cats. Older cats also tend to have shorter lived red blood cells, as do patients with infections or inflammation. Since these factors apply to many CKD cats, it is not too surprising that they are so prone to developing anaemia.

Your vet will usually determine whether your cat has anaemia and how severe it is via a blood test called packed cell volume (PCV). PCV measures the ratio of red blood cells to total blood volume. The blood is spun in a centrifugal machine and your vet measures the total number of cells that are left. It does not distinguish old blood cells from new but it is a still a useful and accurate test for anaemia.

Some vets check haematocrit (HCT) instead, which is very similar to PCV. HCT actually refers to the red blood cells that are left only; but since the other blood cells (white cells and platelets) usually make up less than 1% of blood volume, the difference between PCV and HCT is too small to be concerned about.

Only a small amount of blood is needed for these tests (although more blood is needed for HCT than for PCV) and most vets have the necessary equipment in their offices so you can get a result in a few minutes. Some people test at home (see above).

The PCV test shows if your cat is anaemic, but it does not show whether the anaemia is regenerative or non-regenerative. Regenerative anaemia means that the cat's body may be able to correct the anaemia without any external help, whereas with non-regenerative anaemia, the cat is going to need some help in the form of some kind of treatment.  Many cats with CKD and anaemia are suffering from non-regenerative anaemia caused by problems with production of a hormone called erythropoietin (see Why anaemia occurs in CKD cats) but they may also have other problems contributing to their anaemia.

Reticulocytes Test

This table explains what the various levels of reticulocytes mean. Remember, the table is only  applicable to cats who have severe anaemia (PCV below 20% for five days or longer).

Haemoglobin, the main oxygen-carrying protein of red blood cells, needs iron for its production. Therefore a cat with low iron levels may develop a type of anaemia known as iron-deficiency anaemia.

Since iron is present in food, particularly meat, iron deficiency anaemia from lack of iron in the diet is rare in cats, but may be present for other reasons.

Cats with inflammation or an infection may have an iron deficiency, and both inflammation and infection are associated with CKD. Acute-phase proteins and iron status in cats with chronic kidney disease (2017) Javard R, Grimes C, Bau-Gaudreault L & Dunn M Journal of Veterinary Internal Medicine 31(2) pp457–464 looked at levels of a recently discovered acute phase protein called hepcidin in CKD cats. In human CKD patients hepcidin assists with iron metabolism and plays a role in the development of anaemia. The study concludes "Our data suggest that CKD in cats is associated with systemic inflammation and altered iron metabolism."

Another factor is that, if inflammation or infection are present, the body sequesters (hides away) iron. Iron metabolism in pathogenic bacteria (2000) Ratledge C & Dover LG Annual Review of Microbiology 54 pp881-941 explains more about this.

• Mean Cell Volume (MCV)

• Iron

• Ferritin

• Total Iron Binding Capacity (TIBC)

• MCHC

Mean Corpuscular Volume or Mean Cell Volume (MCV)

This is a measure of red blood cell size.

Cornell University College of Veterinary Medicine has more information about MCV.

Cornell University College of Veterinary Medicine has an MCV calculator.

Normocytic MCV

This means the MCV is normal. This tends to be what you see in CKD cats with non-regenerative anaemia caused by a lack of erythropoietin who do not have an iron deficiency.

Microcytic MCV

This means the MCV is low, indicating the red blood cells are smaller than usual. This may indicate iron deficiency. Possible causes include gastrointestinal bleeding or chronic liver disease.

Low MCV may also be seen in CKD cats. Iron status of cats with chronic kidney disease (2015) Gest J, Langston C & Eatroff A Journal of Veterinary Internal Medicine 29 pp1489-1493 states "TSAT and MCV (mean corpuscular volume)-a microcystosis- were significantly lower in anemic cats compared to non-anemic cats with CKD. This indicates a finding of both an absolute and a functional iron deficiency. The functional anemia is likely secondary to decreased erythropoiesis by diseased kidneys as well as anemia of inflammation."

Microcytosis is also a possible early sign of aluminium toxicity. Aluminium toxicity is extremely rare but may need to be ruled out if you are using aluminium hydroxide phosphorus binders.

Iron

This measures the amount of iron circulating in the blood. This test should be a fasting test, and iron supplements should not be given for 24 hours before the test.

If serum iron is low, the cat may have an iron deficiency, especially if ferritin and TIBC (see below) are also low.

If serum iron is low but ferritin (see below) is normal or high, the cat may have an infection.

If a cat has anaemia of chronic disease (e.g. caused by CKD or Inflammatory Bowel Disease (IBD), the serum iron will be low, TIBC will tend to be low, but ferritin will be normal to high.

Serum iron is normally high if a cat has had a number of blood transfusions. These cats should not be given iron supplements.

Cornell University College of Veterinary Medicine has some information about iron.

Ferritin

This is a measurement of how much iron is stored in the body in soluble form.

Low levels can indicate iron deficiency, especially if iron and TIBC are also low..

High levels can indicate inflammation or iron overload (e.g. from a blood transfusion).

Cornell University College of Veterinary Medicine has some information about ferritin.

TIBC (Total Iron Binding Capacity)

This measures the capacity of the blood to transfer iron to the cells where it is needed. Iron status of cats with chronic kidney disease (2015) Gest J, Langston C & Eatroff A Journal of Veterinary Internal Medicine 29 pp1489-1493 states "total iron binding capacity was found to be significantly lower in CKD cats versus healthy cats." It goes on to say "TIBC is decreased in inflammation. With TIBC significantly lower in cats with CKD compared to healthy cats, this study’s results support the presence of inflammation in this group of CKD cats."

If a cat has an iron deficiency, iron, ferritin and TIBC will be low.

If a cat has anaemia of chronic disease (e.g. caused by Inflammatory Bowel Disease (IBD)), the serum iron will be low, TIBC will tend to be low, but ferritin will be high.

If a cat is suffering from an iron overload, iron levels will be high and TIBC will be low or normal.

Cornell University College of Veterinary Medicine has some information about TIBC.

MCHC (Mean Cell Haemoglobin Concentration)

If your vet cannot check ferritin or TIBC, you can be guided by the MCHC instead. As the name suggests, this measures the concentration of haemoglobin in a red blood cell. You can calculate MCHC as long as you have a measurement for haemoglobin (Hb):

Cornell University College of Veterinary Medicine has some information about MCHC.

If you don't know the cause of your cat's anaemia, your vet will need to consider and rule out possible causes until you know the most likely cause (don't forget there may be more than one cause). Please read above on how to do this.

I would recommend B vitamins for every anaemic cat, whatever the cause.

Other possible treatments include flea treatments if your cat has fleas, antibiotics if your cat has a bacterial infection, treatments for gastrointestinal bleeding such as sucralfate, and corticosteroids if your cat has an autoimmune disease. However, since anaemia is often multifactorial in CKD cats, you will need to remain alert and take action as appropriate.

• Possible treatment plan for CKD cats

  • Vitamin B

  • Diet

  • Erythropoiesis stimulating agents (Epogen, Aranesp etc.)

  • Prolyl hydroxylase inhibitors (HIF-PH Inhibitors)

    • Molidustat (Varenzin-CA1)

  • Iron supplements

  • Blood transfusions

• Making your cat comfortable

• Other treatments

Since this website is intended for CKD cats, here is a table showing the usual treatment protocol for CKD cats with anaemia caused by a lack of erythropoietin. Some of these treatments are also appropriate for cats with other forms of anaemia, for example severe anaemia from any cause may need a blood transfusion.

Even if your cat has anaemia caused by a lack of erythropoietin, you may find that treating for any other problems that are present, such as an infection, helps the anaemia improve to a level where you do not need to reach for an ESA. So if, for example, your cat has a PCV level of 19% but is known to have an infection, you may find that treating the infection is sufficient to raise the PCV above the level where an ESA needs to be considered.

¹ Unless your cat is known to be iron deficient

² Cats without infections can be given iron in any form. Cats with an infection should not be given iron except in the form of heme iron (see below)

³ Iron should not be given to cats who receive blood transfusions

Because B vitamin supplementation is so important for CKD cats, it has its own page here.

Cats who begin treatment with an ESA such as Epogen or Aranesp are usually given iron supplements because the cat's body is busily making new red blood cells, so there is an increased demand for iron to assist with this process. Managing anemia in patients with chronic kidney disease (2011) Chalhoub S, Langston CE Veterinary Medicine May 2011 states "It is advisable to administer iron at the start of ESA therapy and with continued ESA usage to ensure adequate response." ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18 pp219-239 state that if you are using an ESA, "iron supplementation is generally recommended to ensure iron deficiency does not contribute to the anaemia."

If your cat does not respond to an ESA even though you are giving the ESA in sufficient quantities and frequently enough (see ESAs), consider the possibility of low iron levels and check for iron deficiency as explained above. 

Managing anemia in patients with chronic kidney disease (2011) Chalhoub S, Langston CE Veterinary Medicine May 2011 has information about when and how to supplement iron when using ESAs.

Use of erythropoietin and calcitriol for chronic renal failure in dogs and cats (2005) Sanderson S Presentation to the World Small Animal Veterinary Association World Congress explains more about when and how to supplement iron when using ESAs.

Blood Transfusions

How Blood Transfusions Are Performed

Although there are some risks, a blood transfusion is not usually considered to be a major procedure. The blood is taken either from a donor cat provided by the clinic or by a client who has other cats eligible to be donors, or from a blood bank (see below). Whole blood may be used or packed red blood cells.

The blood is fed through an intravenous drip into the cat. Normally the cat only needs to stay at the vet's for 3-4 hours; just long enough to receive the blood (which is given slowly, particularly at the beginning in case of an adverse reaction), and to be monitored for a possible reaction (occasionally diarrhoea and nausea are seen with a poorly matched transfusion, and fever is sometimes seen).

If your cat has a blood transfusion, you should not give him/her any supplements containing iron because there is a risk of iron toxicity.

Blood Transfusion Effectiveness

• The post transfusion increase in PCV (%) will be the volume of donor blood transfused in ml divided by the weight of the recipient cat in kg multiplied by two.

• To take an example: a 4.5kg (10 lb) cat given 50ml of donor blood would be expected to have a post-transfusion increase in PCV of 5.5%, and one given 30ml of blood would be expected to have an increase in PCV of 3.3%.

In an emergency case such as a cat who is going to die anyway without the transfusion (e.g. after a traffic accident), a vet may do a transfusion without checking the blood types, and in the case of the average non-pedigree cat, this will often not result in disaster the first time it is done, though it is far riskier for pedigree cats who tend to have the rarer blood groups. Feline nonregenerative anemia: diagnosis and treatment (2009) White C & Reine N Compendium: Continuing Education for Veterinarians 31(7) ppE8-12 says "Approximately 70% of all cats with type B blood have anti-A antibodies in amounts sufficient to cause an acute hemolytic or anaphylactic reaction to as little as 1 mL of type A blood. In contrast, 35% of all cats with type A blood have anti-B antibodies, but usually in low enough amounts that a transfusion of type B blood results only in reduced RBC survival time and minor transfusion reactions.^"

Therefore if time permits (as it usually does for CKD cats), it is far safer to type or cross-match a  cat's blood type before a transfusion. Unfortunately, blood typing may not be accurate in cats with a PCV or HCT below 10%.

Feline blood typing and transfusion — a practical approach (2006) Kohn B & Weingart C Presentation to the 31st World Small Animal Veterinary Association World Congress has a good overview of blood transfusions.

Typing and Cross-Matching USA

Your vet may be able to arrange this for you. Here are some possibilities.

The donor also has to be healthy and big enough to give blood without any adverse effects for himself/herself — usually a donor must be at least 9-10 lb in weight and have a PCV of over 30%, or ideally over 35%. In addition, a donor usually cannot give blood more often than every two months. If the donor cat meets these criteria, there are usually no side effects for him/her, and it does not appear to be any more stressful than a standard vet visit for either the donor or the recipient, though the donor cat may need to be sedated. In fact, Feline blood donation: description and adverse reactions from 29,201 donation events between 2019 and 2023 (2024) Taylor SS, Ferreira HCM, Cambra AFP, Lo Iacono G, Jeevaratnam K, Mesa-Sanchez I & Ferreira RRF Journal of Veterinary Internal Medicine 38(6) pp3050-3062 found that adverse reactions were rare (0.29%), but more likely to occur if the donor cat was not sedated.

This does not mean there is no risk at all: a member of Tanya's CKD Support Group did very sadly lose her donor cat, who had donated blood previously but who suddenly collapsed and died following a donation. It is thought that he may have had an undiagnosed heart condition.

Alternatively, there are a limited number of feline blood banks which may be able to help, including:

Other Sources of Blood

Since it can be difficult to obtain feline blood, some people are obliged to use alternatives:

Canine Blood

If you are unable to obtain feline blood, and it is an emergency, you can consider using a blood donation from a dog. Xenotransfusion with canine blood in the feline species: review of the literature (2013) Bovens C & Gruffydd-Jones T Journal of Feline Medicine and Surgery 15(2) pp62-7 found that using canine blood may buy you up to four days, but it can only be used once because subsequent use will cause anaphylactic shock, which often kills the cat.

Naturally occurring antibodies in cats against dog erythrocyte antigens and vice versa (2018) Priolo V, Masucci M, Spada E, Proverbio D & Pennisi MG Journal of Feline Medicine and Surgery 20(8) pp690-695 says "This study reveals a high prevalence of naturally occurring antibodies in cats against dog erythrocyte antigens and vice versa, and suggests that transfusion of cats with canine blood is not recommended as a routine procedure owing to the potential high risk of either acute severe or milder transfusion reactions."

Xenotransfusion of canine blood to cats: a review of 49 cases and their outcome (2019) Le Gal A, Thomas EK & Humm KR Journal of Small Animal Practice 61(3) pp156-162 gave canine blood to 49 anaemic cats, ten of whom (20%) died or were put to sleep within 24 hours of the transfusion, though not because of the transfusion effects. A delayed reaction (a couple of days after the trausfusion) was seen in 63% of the remaining cats. However, 18 cats were alive a week after leaving hospital and 15 of those were still alive a median of 173 days later.

The Royal Veterinary College, which undertook the study, reports a little more on the study.

Sadly the manufacturer of Oxyglobin went bust but another company has apparently taken over its production.

The cost of a blood transfusion varies widely, depending upon where you are and how you source the blood. If you have to obtain blood from a blood bank it will cost more, but fresh blood may be available from a donor cat at your vet's, or one of your own cats may be a suitable donor.

The costs will include some or all of the following:

• blood typing and cross-matching

• blood tests such as PCV

• blood cost or provision of donor cat cost

• testing of donor if one is used

• hospital fees, including giving the blood intravenously and post-transfusion care

As a rough guide, one member of Tanya's CKD Support Group in the UK paid £300 in 2014. The approximate fee in the USA is in the region of US$500-1000.

Transfusions for Cats with the Antibody Reaction to ESAs

If your cat has severe non-regenerative anaemia because of CKD but is not yet critical (i.e. the PCV is above 13-15%), I would recommend using ESAs instead of transfusions. By doing this, you can keep transfusions in reserve just in case your cat does develop a reaction to ESAs, at which point you could probably buy your cat some more time by using transfusions.

If your cat does develop a reaction to an ESA such as darbepoetin (Aranesp) or epoetin (Epogen or Eprex), the good news is that this does not increase the chances of your cat developing a reaction to donated blood.

Cats with the antibody reaction to ESAs may need transfusions fairly frequently to start with while the body is dealing with the ESA antibodies, but the period between transfusions may lengthen over time as the ESA antibodies go away (this takes up to eight months, though may take longer in some cats).

• electric beds which maintain a constant temperature. With some you can choose from up to three temperature settings and then the pad stays at the chosen temperature constantly.

• electric beds which only warm up once the cat settles on them. You may be able to choose the temperature settings with this type of bed too.

• non-electric beds which reflect the cat's body heat back, thus keeping the cat warm.

You must of course keep an eye on your cat while s/he is using the electrical type, and I would not use any of these beds for a cat who is incapable of moving if s/he gets too hot. We never had any problems with overheating, and Thomas found his bed very comforting when his anaemia was severe, whilst Harpsie loved his when he developed arthritis.