When to Worry About High Platelet Count

A high platelet count is not always a serious concern

Thrombocytosis, or a high platelet count, is diagnosed when platelet levels are greater than 450,000 platelets per microliter of blood. Many times, a high platelet count doesn’t cause any symptoms or mean something serious is going on. However, having a high platelet count can lead to 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, in two specific genes, the JAK2 gene and the CALR gene.
  • 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 in what circumstances having a high platelet count may or may not be something to worry about.

Normal Platelet Count

A normal platelet count is about 150,000 to 450,000 platelets per microliter of blood.Platelets, also called thrombocytes, are the cells in the blood that help blood clot.

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, as well as 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
  • Mammogram, an imaging test that checks for breast cancer
  • Upper endoscopy, which is a procedure that inserts a small tube with a camera into the mouth and down to the stomach, to check for cancer in the upper digestive tract
  • Colonoscopy, which is a procedure that uses a small tube with a camera that is inserted into the rectum to check for gastrointestinal cancer in the large intestine

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
Potential Complications From High Platelet Count - Illustration by Theresa Chiechi

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 that can be a result of either too high or too low 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 to cause a high platelet count include gastrointestinal cancer, lymphoma, ovarian cancer, lung cancer, and breast cancer.

Less Concerning Possibilities

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:

What Infections Cause High Platelet Count?

Research has found that urinary tract infections, respiratory infections, and gastrointenstinal infections are among the leading causes of a high platelet count.


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 they 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?

The majority of 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 levels. 

However, having a high platelet count can be associated with cancer. One study reported that about 11% of assigned males with high platelets and about 6% of assigned females with high platelets had cancer.


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.

Frequently Asked Questions

  • What causes a high platelet count?

    Sometimes, your body simply makes too many platelets. In other cases, there may be a problem like an infection or anemia. Because some of these problems can be serious, high platelets always need to be thoroughly evaluated by a healthcare provider.

  • Does COVID affect platelet count?

    Yes. Inflammatory proteins produced as a result of COVID-19 infection significantly raise platelet counts and the risk of forming dangerous blood clots. This can lead to heart attacks, strokes, and other serious complications.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Julie Scott, MSN, ANP-BC, AOCNP
Julie is an Adult Nurse Practitioner with oncology certification and a healthcare freelance writer with an interest in educating patients and the healthcare community.