Overview

Platelets are parts of the blood that help form blood clots. Thrombocytosis (throm-boe-sie-TOE-sis) is a disorder in which your body produces too many platelets.

It's called reactive thrombocytosis or secondary thrombocytosis when the cause is an underlying condition, such as an infection.

Less commonly, when the high platelet count has no apparent underlying condition as a cause, the disorder is called primary thrombocythemia or essential thrombocythemia. This is a blood and bone marrow disease.

A high platelet level may be detected in a routine blood test known as a complete blood count. It's important to determine whether it's reactive thrombocytosis or essential thrombocythemia to choose the best treatment options.

Types

  1. Essential thrombocythemia

Symptoms

People with high platelet levels often don't have signs or symptoms. When symptoms occur, they're often related to blood clots. Examples include:

  • Headache.
  • Confusion or changes in speech.
  • Chest pain.
  • Shortness of breath and nausea.
  • Weakness.
  • Burning pain in the hands or feet.

Less commonly, very high platelet levels may cause bleeding. This can cause:

  • Nosebleeds.
  • Bruising.
  • Bleeding from your mouth or gums.
  • Bloody stool.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.

Causes

Bone marrow is a spongy tissue inside your bones. It contains stem cells that can become red blood cells, white blood cells or platelets. Platelets stick together, helping blood to form a clot that stops bleeding when you damage a blood vessel, such as when you cut yourself. Thrombocytosis occurs when your body produces too many platelets.

Reactive thrombocytosis

This is the more common type of thrombocytosis. It's caused by an underlying medical problem, such as:

  • Blood loss.
  • Cancer.
  • Infections.
  • Iron deficiency.
  • Removal of your spleen.
  • Hemolytic anemia — a type of anemia in which your body destroys red blood cells faster than it produces them, often due to certain blood diseases or autoimmune disorders.
  • Inflammatory disorders, such as rheumatoid arthritis, sarcoidosis or inflammatory bowel disease.
  • Surgery and other types of traumas.

Essential thrombocythemia

The cause of this disorder is unclear. It often appears to be connected to changes in certain genes. The bone marrow produces too many of the cells that form platelets, and these platelets often don't work properly. This poses a much higher risk of clotting or bleeding complications than does reactive thrombocytosis.

Complications

Essential thrombocythemia can lead to a variety of potentially life-threatening complications, such as:

  • Strokes. If a blood clot occurs in the arteries that supply the brain, it may cause a stroke. A mini stroke, also called a transient ischemic attack, is a temporary interruption of blood flow to part of the brain.
  • Heart attacks. Less commonly, essential thrombocythemia can cause clots in the arteries that supply blood to your heart.
  • Cancer. Rarely, essential thrombocythemia may lead to a type of leukemia that progresses quickly.

Pregnancy complications

Most women who have essential thrombocythemia have normal, healthy pregnancies. But uncontrolled thrombocythemia can lead to miscarriage and other complications. Your risk of pregnancy complications may be reduced with regular checkups and medication, so be sure to have your doctor regularly monitor your condition.

Thrombocytosis care at Mayo Clinic

Dec. 30, 2022

Living with thrombocytosis?

Connect with others like you for support and answers to your questions in the Blood Cancers & Disorders support group on Mayo Clinic Connect, a patient community.

Blood Cancers & Disorders Discussions

Jackie, Alumna Mentor
Non Hodgkin's Lymphoma- Watch & Wait Approach

197 Replies Thu, Apr 11, 2024

shenriq
Essential Thrombocythemia: Looking for information and support

468 Replies Wed, Apr 10, 2024

Lori, Volunteer Mentor
My Bone Marrow Transplant (BMT/SCT) story: Will you share yours?

330 Replies Tue, Apr 09, 2024

See more discussions
  1. Platelet disorders: Thrombocythemia and thrombocytosis. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health/thrombocythemia-thrombocytosis. Accessed Nov. 30, 2022.
  2. Ferri FF. Thrombocytosis. In: Ferri's Clinical Advisor 2023. Elsevier; 2023. https://www.clinicalkey.com. Accessed Nov. 30, 2022.
  3. Tefferi A. Approach to the patient with thrombocytosis. https://www.uptodate.com/contents/search. Accessed Nov. 30, 2022.
  4. Reactive thrombocytosis (Secondary thrombocythemia). Merck Manual Professional Version. https://www.merckmanuals.com/professional/hematology-and-oncology/myeloproliferative-disorders/reactive-thrombocytosis-secondary-thrombocythemia?query=thrombocytosis. Accessed Nov. 30, 2022.
  5. Tefferi A. Diagnosis and clinical manifestations of essential thrombocythemia. https://www.uptodate.com/contents/search. Accessed Nov. 30, 2022.
  6. Essential thrombocythemia. Merck Manual Professional Version. https://www.merckmanuals.com/professional/hematology-and-oncology/myeloproliferative-disorders/essential-thrombocythemia?query=thrombocytosis. Accessed Nov. 30, 2022.
  7. Kaushansky K, et al., eds. Hereditary and reactive thrombocytosis. In: Williams Hematology. 10th ed. McGraw Hill; 2021. https://accessmedicine.mhmedical.com. Accessed Nov. 30, 2022.
  8. Tefferi A. Prognosis and treatment of essential thrombocythemia. https://www.uptodate.com/contents/search. Accessed Nov. 30, 2022.
  9. Pruthi RK (expert opinion). Mayo Clinic. Dec. 7, 2022.

Related

News from Mayo Clinic

Products & Services