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What are Thrombocytosis?

Thrombocytosis, also known as thrombocythemia, is a serious abnormality affecting the ability of your dog’s blood to clot correctly.  If your dog has thrombocytosis it means he has too many platelets circulating in his bloodstream.  This can lead to altered blood flow and even clot formation within the bloodstream where it should not be.  Symptoms can be vague, such as exercise intolerance and blood in the stool, but lab work will show the increased numbers.  If left untreated, it can lead to clot formation in your dog’s body that ends up in his lungs or heart and can be fatal.

Thrombocytosis is a blood clotting disorder in your pet.  He may not show any symptoms of illness or he may not seem himself.  If you have not done blood work on your dog recently, perhaps discuss performing some with your veterinarian.

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Symptoms of Thrombocytosis in Dogs

Symptoms may include:

  • Blood in the stool
  • Distended abdomen
  • Enlarged spleen
  • Chronic anemia 
  • Weight loss
  • Exercise intolerance


Thrombocytosis is known as an increase in the number of platelets circulating in the blood stream.  Platelets are a part of the blood’s clotting method; this allows a dog’s body to control bleeding when faced with an injury.  Without platelets, the patient would just bleed constantly until he bleeds out.  If there are too many platelets, a clot can form where it should not and possibly lead to a more severe issue or death.

Causes of Thrombocytosis in Dogs

Thrombocytosis is most commonly caused by a response to epinephrine release, a response to a disease in another part of the body, or by a bone marrow related disease.  Thrombocytosis can be temporary as a response to a natural bodily function like pregnancy or birth.  It can also be seen long term with infections or inflammatory disorders.  Medications can also lead to a temporary increase in platelet production.

Diagnosis of Thrombocytosis in Dogs

If your dog is experiencing a type of reactive thrombocytosis, it typically resolves as the infection resolves with time.  It is also natural for your dog to experience a high platelet count after surgery or large injury as it is the body’s natural defense mechanism to ensure proper clot formation.

If the increased platelet numbers were found on routine blood work, your veterinarian may recommend further diagnostics to confirm or rule out other possible causes of his symptoms.  If there is blood in his stool, she will recommend a fecal flotation and possibly a smear.  This can rule out intestinal parasites and a bacterial overgrowth, both of which could cause the blood in the stool.  If his abdomen is distended, she may recommend radiographs to see how the internal organs look.  With the radiograph, she will be able to see if there are any abnormalities regarding the organs, including an enlarged spleen.  If a radiograph is not enough, she may recommend having an ultrasound performed as well.  An ultrasound provides the veterinarian with more detailed imaging than a radiograph alone.  

If the veterinarian suspects an underlying disease as the cause of the thrombocytosis, she will need to run further diagnostics to confirm.  A chemistry panel and complete blood count are the basic blood tests she will start with.  If she suspects a disease related to the bone marrow, she will have to take a sample of the marrow to examine it.  If there is an increase in megakaryocytes, then it is a bone marrow related disease.

Treatment of Thrombocytosis in Dogs

The cause of your dog’s thrombocytosis will determine his course of treatment.  The veterinarian needs to determine the underlying cause and treat that versus just his thrombocytosis.  If your dog has cancer, you will need to treat and beat it in order to stop the increased production of platelets.  If it is a medication causing it, stopping the medication in a safe manner is ideal.

In the meantime, there are medications like aspirin and similar anticoagulants that can be prescribed to decrease platelet clotting.  However, this can come with its own side effects.  If your dog is ever injured, the time it takes his blood to clot can be delayed; this can lead to severe blood loss.

Supportive therapies can be administered as your veterinarian sees fit.  She will want to ensure his appetite remains healthy as he fights off disease, verify that he is drinking enough water, and determine that he has no other medical issues to be cured at the same time.  For example, your veterinarian will want to make sure your dog is on a flea prevention at all times to prevent blood loss and clotting activation series due to constant flea bites.  It may seem simple, but it can have a large impact on a sick pet.

Recovery of Thrombocytosis in Dogs

If there are complications from the thrombocytosis, prognosis of recovery is guarded to poor.  For example, thrombocytosis can lead to altered blood flow causing certain vital organs to not receive enough blood to keep functioning properly.  Or your dog can develop a clot and have it end up in his lungs or heart which can lead to him not being able to breathe, or his to heart stop.  However, if you and your veterinarian are able to get the underlying issue resolved and your dog’s platelet count back to normal, his prognosis is fair to good.

Thrombocytosis Questions and Advice from Veterinary Professionals

minature schnauzer
14 Years
Mild condition
0 found helpful
Mild condition

Has Symptoms

High platelets and liver enzymes.

My 5 pound 14 yr old schnauzer has had high platelets for a couple years. My Vet doesn’t seem concerned. Should I be? She eats well and acts fine for a senior dog. She has had elevated liver enzymes since a puppy and we keep her on prescription liver dog food and she’s fine.

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7 Years
Moderate condition
0 found helpful
Moderate condition

Our yorkie recently has very high platelets (over 15,000). She has protein losing enteropathy and has been taking prednisone and azathioprine along with iron drops. Could the iron drops have caused the high platelet count?

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17 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

See above low mobility hind legs. T

My 17 y.o. has high platelet count. Terrier spitz mix. Wt,29#. Has bladder tumor,low mobility. On compound med nonsteroid add another med,neurotin. Chronic bladder infection resistant to all antibiotics used and on decision. Any ideas?

Dr. Michele King, DVM
Dr. Michele King, DVM
1611 Recommendations
A high platelet count is often an incidental finding, and rarely cause for concern. Without knowing more about Destin, I can't comment on an isolated lab result, but if you are concerned, it would be best to call your veteirnarian and ask if you have any reason to worry about that one finding.

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Cocker Spaniel
7 Years
Serious condition
1 found helpful
Serious condition

Has Symptoms

Platelet count over 1 million

Medication Used

Vincristine in March, 2017

My cocker spaniel had his spleen removed February 24, 2017. It was determined he has Leiomyosarcoma.

A month later his platelet count fell to 700. They gave him Vincristine.

Now his platelet count is over 1 million and has not come down. It has been that high since end of March.
Is this serious and what can I do?

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3320 Recommendations

Cancer is the most common cause of an increase in blood platelet levels; where a tumour in the spleen can lead to platelet damage resulting in a lower platelet count, you remove the tumour and the platelet count increases. An increase in thrombocyte count can be managed with some medications, however these may be contraindicated in this case; further investigation is required to determine the best course of treatment, you may need to visit an Oncologist to get a better picture of your options. Regards Dr Callum Turner DVM

Thank you!

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