High Platelets: Levels, Causes, Related Symptoms, and More

Medically Reviewed By Brett Barlow, MD

Having high platelets means that the blood contains more platelets than is typically expected. Platelets are blood cells responsible for making the blood clot. If your platelet levels are too high, blood clots can form in your blood vessels and block the flow of blood around the body. High platelet levels can be a sign of an underlying condition. This means that an existing illness is causing the body to produce more platelets than necessary.

When high platelets occur as a result of another condition, this is called thrombocytosis.

This article explains what high platelet levels mean, symptoms, testing and results, treatment, and more. It also discusses the causes of high platelets, including thrombocytosis and thrombocythemia.

What does it mean if your platelet count is high?

A person's arm rests on a clinician's table with a tourniquet around the upper arm. Gloved hands wipe the inner arm with a sterile wipe.
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High platelets is a condition in which the blood contains more platelets than usual.

Platelets, or thrombocytes, are small blood cell fragments that assist in blood clotting and help stop bleeding. Clinicians can identify a high platelet count through routine blood tests.

A high platelet count can indicate an underlying condition. However, it can also occur spontaneously, meaning that it happens on its own and not as an effect of another illness. Spontaneous high platelets can still present a risk to health due to the risk of blood clots forming.

Because of this, clinicians categorize the occurrence of high platelets into two medical categories. These are thrombocythemia and thrombocytosis.


Thrombocytosis, also known as secondary or reactive thrombocytosis, is when high platelets occurs as a symptom of another disease or condition. It can result from anemia, infection, or cancer.


Thrombocythemia is when the cause of high platelets is unknown. It occurs as an independent condition.

Clinicians may also refer to thrombocythemia as primary or essential thrombocythemia. Researchers believe that it may be the result of gene mutations.

The condition is not very common, but it may occur more frequently in people ages 50–70 years. That said, it can happen at any age. Thrombocythemia is also more common in people assigned female at birth than those assigned male.

Testing and typical platelet levels

An expected platelet range in a healthy individual is 150,000–400,000 platelets per microliter (mcl) of blood. Your exact number may fluctuate day to day.

The average platelet count for females is up to 371,000 per mcl of blood. The average count is up to 317,000 per mcl of blood for males.

If your platelet count is higher than average or outside the expected maximum of 400,000 per mcl of blood, this could indicate an underlying condition.

Clinicians classify a platelet count of more than 450,000 per mcl of blood as thrombocytosis.

High platelet count symptoms

In many cases, high platelets may not cause symptoms. In these cases, it is possible that clinicians only detect high platelets through routine blood tests.

In other cases, the elevation in platelet levels leads to the development of unnecessary blood clotting throughout the body. This can produce a number of symptoms.

Thrombocytosis may also present with other symptoms, which vary depending on the underlying disease, disorder, or condition. You may be experiencing the symptoms of the primary underlying disorder.

For example, if your thrombocytosis is the result of anemia, you may first notice some symptoms of anemia, such as fatigue.

Symptoms of high platelet counts

Symptoms of thrombocytosis and thrombocythemia often include signs of bleeding and blood clots.

General symptoms can include:

  • headaches or migraine
  • dizziness
  • numbness
  • redness or flushed skin
  • a sensation of burning or throbbing pain
  • itching
  • fatigue
  • bleeding without trauma or injury, such as from nosebleeds or from the mouth or gums
  • bruising
  • blood in your stool
  • an enlarged spleen or liver, causing feelings of fullness, indigestion, stomach pain or discomfort, and appetite loss
  • unexplained weight loss

Because blood clots very often develop in the hands and feet, these symptoms may be particularly present in the palms of the hands or soles of the feet. However, clots can occur anywhere in the body.

You may be more likely to experience a blood clot if you are older, smoke, have other health conditions such as diabetes or high blood pressure, or have experienced blood clots before.

When to seek medical help

Although not everyone experiences additional symptoms, some symptoms are severe and can present a significant risk to health or life.

Symptoms of blood clots may require emergency care

Blood clots can present life threatening effects.

Seek emergency treatment or call 911 for anyone experiencing the following symptoms of blood clots:

Get immediate medical help for bleeding that does not stop or improve.

Learn more about stroke.

What causes high platelets?

Platelets are made in the bone marrow, which is the tissue located inside of bones.

High platelet counts can result from faulty bone marrow cells making too many platelets. These platelets may also be faulty and not function as they should.

Causes of thrombocythemia

With thrombocythemia, excess platelet production can onset spontaneously, independent of another condition.

Clinicians are not completely sure what causes this to happen. However, it often occurs due to genetic factors. When genes mutate, or change, this can affect how the bone marrow forms platelets, causing thrombocythemia.

Thrombocythemia is also inheritable, meaning that it is possible to pass the condition on to your children.

Causes of thrombocytosis

Thrombocytosis is the occurrence of high platelets as a symptom of another condition.

A wide range of diseases and conditions can cause high platelets, including:

  • anemia, such as from iron deficiency or hemolytic anemia
  • cancer, particularly lymphoma, gastrointestinal cancer, breast cancer, or ovarian cancer
  • chemotherapy
  • surgery
  • splenectomy, or surgical removal of the spleen
  • an adverse reaction to a medication or to exercise
  • an allergic reaction
  • an infection
  • stress and anxiety
  • inflammation and inflammatory diseases, such as Kawasaki disease
  • tissue damage
  • myelodysplasia, which refers to a group of conditions in which the blood cells develop or function atypically
    • One example is polycythemia vera. It is a disorder of the bone marrow that causes an excess of blood cells.

Some causes of thrombocytosis may only cause high platelets for a relatively short amount of time while the body recovers. These causes may include:

  • severe blood loss
  • chronic alcohol consumption
  • low levels of folate or vitamin B12
  • short-term infection or inflammation

Smoking may also be Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source a risk factor for developing thrombocytosis.

Diagnosing the cause of high platelets

If you contact your doctor regarding symptoms of bleeding, blood clots, or other related conditions, they may suggest a blood test.

A test called a complete blood count will measure your levels of blood cells, including platelets, to determine if your levels are appropriate.

Other tests to investigate high platelets or thrombocytosis include:

  • a blood smear test
  • a bone marrow test
  • genetic testing

Your doctor will also ask for your medical and symptom history as well as any relevant family medical history.

Additionally, after confirming a high platelet count, your doctor may ask for further tests or refer you to a specialist to investigate the underlying cause.

How is a high platelet count treated?

Some people who experience thrombocythemia and have no symptoms or related underlying conditions may not need treatment.

However, some cases may require clinical care. Although treatment cannot cure your condition, it can help reduce the risk of blood clots and other serious complications.

Medications such as aspirin, hydroxyurea, interferon alfa, and anagrelide are available to treat high platelet counts. Aspirin may help prevent blood clots, while other medications may lower your platelet count.

As interferon alfa and anagrelide medications can both have serious side effects, your doctor may first recommend trying aspirin or hydroxyurea to treat your condition.

Plateletpheresis, also known as platelet reduction apheresis, can quickly lower the number of platelets in the blood.

Doctors will use an IV needle to remove blood from the blood vessels. A machine will then remove the platelets from the blood. Another IV line will then send the treated blood back into your body. Clinicians typically only use this procedure in emergencies.

How is thrombocytosis treated?

Since thrombocytosis is the result of an underlying condition or cause, doctors will aim to treat the original condition that causes high platelets as a secondary effect.

Clinicians may also treat the direct symptoms of thrombocytosis. They will either administer medications to prevent blood clots and reduce your platelet count or recommend plateletpheresis.

What are the potential complications of high platelets?

Because high platelets can be the result of a serious disease, a lack of treatment or ineffective treatment may result in serious complications and permanent damage.

Once a doctor diagnoses the underlying cause, it is important for you to follow the treatment plan that they design specifically for you to reduce the risk of further complications.

Potential complications of high platelets may include:

It is also important to note that complications from blood clotting in thrombocytosis can be rare.

Other frequently asked questions

Here are some additional commonly asked questions about high platelets.

When should you worry about a high platelet count?

If you have had a blood test result that indicates a high platelet count, ask your doctor about the meaning of your results and about any precautions or treatments you should take.

Seek emergency medical treatment for symptoms of blood clots or uncontrollable bleeding. However, complications from thrombocytosis can be rare.

Can stress cause high platelets?

Yes, stress and anxiety can affect platelet counts and activity, leading to high platelets. This is relatively typical.

If you are worried about the impact of stress and anxiety on your health, contact your doctor to discuss your treatment and management options.

Can high platelets make you tired?

High platelets can make you feel tired or fatigued.

This can happen due to thrombocythemia and thrombocytosis. Or, in cases of thrombocytosis, you may also feel tired as a symptom of the original underlying condition and cause.

What kinds of infections cause high platelets?

High platelets from thrombocytosis may be the result of a bacterial, viral, or fungal infection.


High platelets refers to when there are high amounts of platelets in your blood. Clinicians consider platelet counts to be high when they are above 400,000 per mcl of blood.

As platelets are responsible for blood clotting, a high platelet count can present a risk to health due to the formation of unnecessary blood clots in the body.

When high platelets occur spontaneously and as a result of genetic changes, it is known as thrombocythemia.

When high platelets occur as a symptom of another underlying condition or cause, it is known as thrombocytosis. These underlying conditions and causes can include infections, anemia, cancer, and certain medications.

Treatment for both causes of high platelets is similar and focuses on preventing blood clots and further complications. It can involve medications or a blood replacement procedure called plateletpheresis.

Contact your doctor to ask about a blood test or to get more advice about your test results.

Seek emergency medical treatment for any symptoms of blood clots, such as confusion, sudden pain, difficulty seeing, and a loss of consciousness.

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Medical Reviewer: Brett Barlow, MD
Last Review Date: 2022 Jun 17
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