Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at July 26, 2016

Thrombocytosis is defined as one of two myeloproliferative disorders that cause the body to overproduce platelets (also known as thrombocytes). Produced in the bone marrow, platelets are blood cells that are responsible for coagulation – that is, creating blood clots that help heal injuries. A patient with thrombocytosis in which the cause is genetically based or unknown is said to have primary or essential thrombocytosis (also known as thrombocythemia). When a high platelet count occurs alongside or as a result of an underlying disease or injury, it is known as secondary or reactive thrombocytosis.


Definition & Facts

Primary thrombocytosis is a disorder characterized by a higher than normal platelet count and often has underlying genetic components. Secondary or reactive thrombocytosis occurs in the presence of another disease or disorder such as an iron deficiency or a vitamin deficiency or a kidney disease. This type is relatively benign. Reactive thrombocytosis may also occur as a result of an injury, trauma or surgery.

Some estimates posit that there are 6,000 cases diagnosed annually in the United States. However, the actual number of cases may be higher, as many people who are affected by it are unaware of their condition. People over the age of 60 are at a higher risk for this disease.

Symptoms & Complaints

Thrombocytosis causes very few symptoms, and the symptoms that do occur most often stem from underlying diseases such as lymphoma or another disorder of the bone marrow. In some cases of secondary thrombocytosis, however, a patient may present with headaches, dizziness, chest pain and bodily weakness.

Thrombocytosis may also be the direct cause of sudden fainting, temporary changes in vision and numbness in the hands and feet. Whereas secondary thrombocytosis is less dangerous, primary thrombocytosis can lead to abnormal or excessive clotting, and stroke and heart attack may occur. In rare cases, it can lead to leukemia.

In women with essential thrombocytosis, it is known to slow or stop intrauterine growth and to be a direct cause of spontaneous abortion (miscarriage) of the fetus. Babies born to women with essential thrombocytosis may be premature and have low birth weights. Much rarer is excessive bleeding during delivery. 


Conditions of the bone marrow are the number one cause of primary or essential thrombocytosis. Having this type puts the patient at the highest risk level for bleeding and clotting problems. The most common causes of secondary thrombocytosis are infections, trauma, and surgery.

A number of blood and/or bone marrow diseases will bring about this disorder as well. Kidney and gastrointestinal diseases, as well as an enlarged spleen (splenomegaly) and the removal of the spleen (splenectomy) may also directly create high platelet counts. In about 30 percent of cases, a patient's thrombocytosis is linked to cancer.

Extremely vigorous exercise has been cited as a rare cause of this disorder. High platelet counts may also occur if a patient presents with an allergic reaction, an iron deficiency, or a vitamin deficiency. Certain medications, such as heparin sodium, tretinoin, and epinephrine may also trigger reactive/secondary thrombocytosis. 

Diagnosis & Tests

Routine blood tests or blood smears help to determine a diagnosis of secondary or reactive thrombocytosis. Doctors may also order a CBC (complete blood count test) to determine blood platelet count. A physical examination may be performed as well as a test for the presence of too much or not enough iron in the blood, especially if the patient has a bleeding peptic ulcer or other related gastric problem.

Testing for inflammation, blood disorders, and bone marrow disorders will also rule out cancer. If more tests are needed, doctors may order a needle biopsy of the bone marrow. A patient receiving the diagnosis of secondary thrombocytosis should not be overly worried over a temporary rise in platelet count due to the plethora of factors, such as recent surgery or injury, that can bring it about. Only in rare cases is this a life-threatening disorder on its own. 

Treatment & Therapy

Treatment for thrombocytosis is highly individualized and is aimed first at lowering the platelet count. Secondary thrombocytosis often does not need any medication or complicated procedures to reverse it because the chance of blood clotting or bleeding is very low. Once the patient heals from the injury or surgery that brought about the disorder their platelet count will go back to being within a normal range. In other words, once the underlying problem is under control, symptoms of reactive thrombocytosis will end.

If the high platelet count is causing problems with excessive clotting, small doses of aspirin may be prescribed. Other medications used to treat thrombocytosis include hydroxyurea, anagrelide, and ruxolitnib. In the case of a splenectomy, a patient will experience thrombocytosis for the rest of their life, but it is usually not life-threatening nor will it require medication or treatment. 

Prevention & Prophylaxis

According to the National Heart, Lung and Blood Institute, a person can control many of the factors that aggravate primary thrombocytosis even though the disorder itself cannot be prevented. People with a prior history of blood clots, high blood pressure, diabetes mellitus, and who are smokers are at increased risk for complications from the disorder, and lifestyle changes such as healthy diet and regular exercise can address these risk factors.

If the patient has had blood clots before, any related symptoms should be reported to their doctor right away. Reactive thrombocytosis often disappears once the underlying cause is managed. 

People with primary or reactive thrombocytosis often find that their lives do not change much once they are diagnosed with the disorder. Management of symptoms and careful self-evaluation plus maintaining a healthy lifestyle are the best ways to live with thrombocytosis.