Hemophilia in Cats

Hemophilia at a glance

  • About: Hemophilia is an acquired or congenital blood disorder in which the blood doesn’t clot properly due to a lack of clotting proteins (coagulation factors).
  • Symptoms: Excessive bleeding, bruising under the skin, and in severe cases, anemia can develop.
  • Diagnosis: A variety of blood clotting tests.
  • Treatment: Avoid surgery unless necessary, blood transfusions and vitamin K.

What is hemophilia?

What is hemophilia?

Hemophilia is a bleeding disorder in which the blood doesn’t clot properly; it is the most well-known bleeding disorders to affect cats.

When a wound occurs, coagulation (or clotting) occurs to turn the liquid blood into a gel to form a clot and stop blood loss, this is called hemostasis, and there are three steps in this process.

Primary hemostasis

Secondary hemostasis

  • Vasoconstriction:When a blood vessel becomes damaged, vasoconstriction occurs, making the blood vessel smaller, which restricts the loss of blood from the damaged site.
  • Platelet adhesionWhen damage to a blood vessel occurs, circulating platelets form a clump over the damaged vessel to block it off.


  • Coagulation cascade: Fibrinogen is activated by clotting proteins known as coagulation factors in
    the blood-forming fibrin strands. These strands help to mesh the platelet plug, strengthening it.
  • Coagulation factorsThere are 13 coagulation factors from 1 – 13 in Roman numerals. If any of these 13 coagulation factors is deficient or missing, hemophilia can occur. 

Most cats with hemophilia have inherited it (inherited coagulopathies); however, it is also possible for a cat to develop hemophilia at any time in a cat’s life (acquired coagulopathies).


Inherited coagulopathies:

Hemophilia is usually inherited as an X linked recessive trait. Males are most affected as the faulty gene is on the X chromosome, as males only have one X chromosome, he develops the condition.

Female cats have two X chromosomes (one from each parent), which means they can carry the faulty chromosome, but won’t develop hemophilia themselves as their ‘normal’ X chromosome is enough to prevent hemophilia.

While males are most often affected, it is possible for a female to have hemophilia if a male with hemophilia mates with a female carrier, and the two X female chromosomes both have the faulty gene.

Acquired coagulopathies:

Hemophilia can also develop as a result of vitamin K deficiency. This vitamin plays a vital role in the synthesis of coagulation factors in the liver; this is most often due to the ingestion of rat poison.

Liver disease as the liver is responsible for the synthesis of coagulation factors.


  • Hemophilia A: Factor VIII deficiency, is the most common form of hemophilia in cats and is due to a deficiency of coagulation factor 8.
  • Hemophilia B: Factor IX deficiency (sometimes called Christmas disease) and is reported to be inherited in British Shorthair cats.
  • Factor XII (Hageman factor) deficiency: This form of hemophilia typically does not express a bleeding tendency and is usually an incidental finding when routine blood coagulation testing reveal a very long activated partial thromboplastin time (APTT). [1]

A breed predisposition has been linked to Devon Rex, British Shorthair, Siamese and Maine Coon cats and has been seen in domestic cats.


Symptoms of hemophilia usually present before the cat reaches adulthood. Bleeding may occur due to a trauma such as a scratch or a wound. The severity of bleeding depends on the amount of clotting factor missing from the cat’s blood. Kittens with a severe deficiency in affected factors often die at birth.

  • Protracted bleeding following injury and/or surgery that may first occur when the cat is spayed or neutered. Bleeding is usually milder in cats with hemophilia B.
  • Prolonged oral bleeding when the baby teeth are replaced by adult teeth.
  • Bruising and swelling under the skin due to hematomas. These often go unnoticed due to the cat’s fur covering most of the skin.

Other symptoms due to anemia or internal bleeding may also be present and include:

  • Severe weakness
  • Lethargy
  • Pale mucous membranes
  • Blood in the vomit or stool
  • Bleeding from the nose, rectum, gums
  • Swelling in the abdomen due to internal bleeding
  • Limping due to bleeding into the joints
    Rapid breathing
  • Difficulty breathing
  • Loss of appetite


Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you.

Diagnostic workup:

  • In vivo bleeding time: This test involves either cutting the nail just slightly into the quick or pricking the nose to determine how long it takes for bleeding to stop.
  • Coagulation assays: A series of tests to measure clotting time and include: aPTT (activated partial thromboplastin time).
  • Prothrombin time: A test to measure the time it takes for the blood to form a blood clot (thrombus). Plasma (the clear portion of blood) is added to a calcium chloride and thromboplastin agent and a measurement of the time it takes for a clot to form in seconds.
  • Thrombin clotting time: A test that measures the time it takes for a clot to form in plasma in a sample. Bovine thrombin is added to plasma in a test tube and the time between the addition of thrombin and clot formation is measured.
  • Fibrinogen test: A group of tests to measure fibrinogen (fibrinogen antigen test) and assess if it is able to properly form blood clots (fibrinogen activity test).
  • Baseline tests: Biochemical profile, complete blood count, and urinalysis.


There is no cure for cats with inherited hemophilia and treatment will depend on the severity of the disease. Cats with severe hemophilia may need whole blood if anemic or plasma to replace active coagulation factors. Avoid surgery where possible, and if it is necessary, give a blood transfusion prior to surgery.

Acquired hemophilia due to rodenticide poisoning:

If ingestion was recent, the veterinarian will induce vomiting and administer activated charcoal to prevent further absorption, vitamin K will be given via injection followed by long-term (30-45 days) of oral vitamin K.

Home care and prevention

Affected cats should be spayed or neutered and kept inside to prevent the risk of accidents. Avoid strenous active play to reduce the risk of bleeding into the joints. Do not administer medications with anticoagulant properties such as NSAIDs. Maintain excellent dental care to prevent gum disease, which can lead to excessive bleeding of the gums. 


The prognosis is good for cats with mild to moderate hemophilia, however, it is poor in cats with severe hemophilia.

[1] Dr Lowell Ackerman Cat Health Encyclopedia, p. 151
Blood clot image courtesy Michael Tam.


  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio