When to Worry About High Platelet Count


Thrombocytosis, or a high platelet count, is diagnosed when platelet levels are greater than 450,000 platelets per microliter of blood. It’s not always obvious when to worry about a high platelet. Many times, a high platelet count isn’t serious and may not cause symptoms. However, having a high platelet count can lead to blood clotting problems and, in some cases, may be associated with serious conditions like cancer.

The two types of thrombocytosis are primary thrombocytosis and secondary thrombocytosis:

  • In primary thrombocytosis—also called essential thrombocythemia—the bone marrow makes too many platelets. This may be caused by mutations or genetic changes. JAK2 and CALR are the two most commonly mutated genes linked to this condition.
  • Secondary thrombocytosis, also called reactive thrombocytosis, occurs when the platelets increase in response to a condition, infection, medications, or bleeding.

A high platelet count may be found during routine blood work and more tests may be done to diagnose any associated conditions. Treatment will vary depending on the underlying cause, and in some cases, may not be necessary.

This article discusses the diagnosis process and treatment options for a high platelet count and any associated underlying conditions. It also covers when to worry, or not worry, about a high platelet count.

What Do Healthcare Providers Look For?

When determining whether or not a high platelet count is something to worry about, healthcare providers may look for symptoms like bruising, bleeding, and signs of infection or another underlying condition.

It is likely that blood tests or imaging will be done. These tests may include:

  • Iron panel to show how much iron is present
  • Complete blood count, which is a full blood panel that includes white blood cell and red blood cell count
  • C-reactive protein and erythrocyte sedimentation rate blood tests to see if inflammation is present, which would indicate if the body is trying to heal from an infection or injury
  • Blood testing to check for specific gene mutations
  • Bone marrow biopsy, which removes a sample of bone marrow for evaluation
  • Cancer screening tests, if indicated

When a High Platelet Count May Be Concerning

A high platelet count may be worrisome if:

  • You are at risk of developing blood clots, which are linked to primary and secondary thrombocytosis
  • You are pregnant
  • You are showing signs of cancer

Verywell / Theresa Chiechi

Blood Clots

In general, blood clots tend to be linked to primary thrombocytosis. However, they can also occur with secondary thrombocytosis.

Certain individuals are more at risk of developing clots, including those who:

  • Are pregnant
  • Have recently had surgery
  • Have a family history of blood clots
  • Have cancer
  • Are undergoing cancer treatment

Blood clots may form in any blood vessel and prevent blood from flowing properly. Most commonly, they form in the blood vessels in the arms and legs, or in the brain. This decreased blood flow can cause symptoms including:

  • Headaches
  • Dizziness
  • A stroke, which is a medical emergency that occurs when a clot blocks the flow of blood and oxygen to the brain
  • Throbbing pain or numbness
  • A seizure, which is a medical emergency that occurs when the brain cells suddenly have too much activity

If you have a high platelet count and are worried about the risk of developing blood clots, talk to your healthcare provider. 

High Platelet Count in Pregnancy

During pregnancy, sometimes platelet levels can become too low or too high. In some cases this is due to a problem that existed prior to pregnancy; in others, it comes on during pregnancy.

A very high platelet count can cause blood clots that can block blood flow to the embryo or fetus, while low platelet counts can cause bleeding.

Complications associated with high platelet levels include:

In most cases, platelet levels can be managed by getting routine medical care during pregnancy. If platelet levels are too high, it may be necessary to take anti-clotting medications until the fetus is safely delivered. Delivering the fetus early may also be recommended.


Cancer is linked to both primary and secondary thrombocytosis. Cancer can cause secondary thrombocytosis, which may be one of the first signs of certain types of cancer. On rare occasions, primary thrombocytosis can turn into certain types of cancer.

A high platelet count is associated with certain kinds of cancer, including:

The most common cancers that cause a high platelet count include gastrointestinal cancer, lymphoma, ovarian cancer, lung cancer, and breast cancer.

Less Concerning Causes of High Platelet Count

A high platelet count may be less worrisome if it is associated with:

  • Short-term conditions, such as an infection or inflammation
  • Exercise
  • Stress
  • An infant or child
  • Anemia
  • Surgery or trauma
  • Medication usage

While these conditions and circumstances tend to result in a high platelet count returning to normal, if these aren’t treated, monitored, or managed appropriately, they can lead to more concerning risks.

Short-Term Conditions

Certain short-term conditions can lead to a high platelet count. However, this is temporary, with platelet counts tending to return to normal quickly. Examples include:


Exercise can impact platelet count and function. This is thought to do with the release of epinephrine, or adrenaline. When this stress hormone is released, it impacts several organs, including the spleen, which filters blood and stores platelets. Research notes that:

  • Short-term, strenuous exercise can cause an increase in platelet count.
  • Regularly exercising decreases or prevents platelet activation during short-term, strenuous exercise.
  • Regularly exercising helps maintain platelet function when at rest.

Can Stress Cause a High Platelet Count?

Mental stress can impact platelet count and function. Research suggests:

  • Short-term stress is associated with changes in platelet function.
  • Long-term stress is associated with a high platelet count.
  • Short and long-term stress is associated with platelet aggregation, which is when platelets group together near an injury site. This can increase the risk of blood clots.

High Platelet Count in a Child

Pre-term infants are often born with high platelet counts. In most cases, this is not something to worry about as it tends to resolve on its own a few weeks after birth. In older children, high platelet counts are usually a result of infection and also resolve once the infection passes.


There are many types of anemia, a condition in which your blood doesn’t have enough healthy red blood cells. In particular, iron-deficiency anemia and hemolytic anemia can lead to a high platelet count. Treating the anemia should help return your platelet levels back to normal.

Surgery or Trauma

Surgeries and trauma can lead to a high platelet count. For example, spleen removal surgery, or a splenectomy, is significantly associated with secondary thrombocytosis, impacting up to 90% of individuals who undergo this procedure. Associated high platelet levels tend to last about three months before they return to normal.


Taking certain medications is associated with high platelet counts, which is referred to as drug-induced thrombocytosis. These may include:

Be sure to tell your healthcare provider about all medications you are taking.

How Do You Treat a High Platelet Count?

Treating a high platelet count starts with finding the underlying cause. In some cases, if there are no symptoms, no treatment may be required.

Treatment for essential thrombocythemia may include certain medications that slow down the production of platelets. In secondary thrombocytosis, treating the underlying condition, like an infection, may be all that is needed to decrease high platelet levels.

What Is the Outlook for Those With High Platelet Counts?

Most high platelet counts are caused by a reactive process such as infection or inflammation. Once the underlying cause resolves or is managed, platelet counts generally return to normal. 

However, having a high platelet count can be associated with cancer. A 2017 study compared 40,000 people with high platelets to 10,000 people with normal platelets and found that a high platelet count is associated with cancer risk.

Specifically, males with high platelet counts were found to have an 11.6% incidence of cancer, compared to 4.1% for those without. In females, the incidence was 6.2% for those with high platelet counts, and 2.2% for those without.

For people who still had high platelet counts six months later, the incidence went up to 18.1% for males and 10.1% for females. Lung and colorectal cancer were the two most commonly diagnosed cancers in people with thrombocytosis.


Having a high platelet count, or thrombocytosis, doesn’t always indicate something serious is going on. Many times, it is linked to a temporary condition or circumstance, such as an infection or recent surgery. However, high platelet levels can be associated with more serious conditions, such as cancer.

Treatment for elevated platelet levels will vary depending on the underlying cause. In some cases, no treatment may be required.


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