High Platelets

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What is high platelets?

High platelets is a condition in which the blood contains more platelets than normal. Platelets are small blood cell fragments that assist in blood clotting. In a healthy person, there are usually 150,000 to 450,000 platelets per microliter of blood. A high platelet count can be identified through routine blood tests.

The occurrence of high platelets is divided into two medical categories: primary thrombocythemia and secondary thrombocytosis. In primary thrombocythemia, the cause of the high platelets is not known, and it occurs as an independent condition. In secondary thrombocytosis, high platelets occurs as a symptom of another disease or condition, such as anemia, infection or cancer.

In many cases, high platelets may not produce specific symptoms. In other cases, the elevation in platelet levels leads to the development of unwanted and unnecessary blood clotting throughout the body, which can produce a number of symptoms.

The presence of high platelets is rarely associated with a medical emergency. However, in some cases, high platelets may cause blood clotting, bleeding or stroke. Seek immediate medical care (call 911) if high platelets are accompanied by a persistent headache, difficulty breathing, dizziness, seizures, changes in speech, or confusion or loss of consciousness for even a brief moment.

If your high platelets condition is persistent or causes you concern, seek prompt medical care.

What other symptoms might occur with high platelets?

High platelets may accompany other symptoms, which vary depending on the underlying disease, disorder or condition. However, some people who have high platelets may not experience any other symptoms. In these individuals, high platelets may only be detected through routine blood tests.

People with primary thrombocythemia have a higher risk of bleeding and blood clots than those with secondary thrombocytosis.

General symptoms that may occur along with high platelets

Generalized symptoms that may occur with high platelets include:

  • Bleeding
  • Headache
  • Numbness of hands or feet
  • Weakness

Bleeding symptoms that may occur along with high platelets

Symptoms of abnormal bleeding include:

  • Bleeding in mouth or gums
  • Bloody stool (the blood may be red, black, or tarry in texture)
  • Easy bleeding or bruising
  • Nosebleeds

Blood-clotting symptoms that may occur along with high platelets

The extremities and the brain are common sites for blood clot formation with high platelets. Clots can also form in other organs. Blood clots in the placenta often cause pregnancy loss in pregnant women with primary thrombocythemia. Signs and symptoms of blood clotting, which may be serious or even life threatening, can include:

  • Changes in speech
  • Confusion or loss of consciousness for even a brief moment
  • Difficulty breathing
  • Dizziness
  • Intense burning and throbbing pain in arms or legs
  • Nausea
  • Pain in the jaw, abdomen or neck
  • Seizures

Serious symptoms that might indicate a life-threatening condition

In some cases, high platelets may accompany symptoms of blood clotting, which may cause a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these potentially life-threatening symptoms including:

What causes high platelets?

Platelets are made in bone marrow, the tissue located inside of bones. Abnormally high platelet production may occur independently, for reasons that are not known (primary thrombocythemia), or as a symptom of another condition (secondary thrombocytosis).

Causes of high platelets in primary thrombocythemia

Thrombocythemia is a condition in which high platelets occur as an independent condition without another known cause. In this condition, the bone marrow makes too many platelets. This condition may be inherited.

Causes of high platelets in secondary thrombocytosis

Thrombocytosis is the occurrence of high platelets as a symptom of another condition. A wide range of diseases and conditions may cause high platelets including:

  • Anemia (low red blood cell count)

  • Blood loss

  • Cancer

  • Chemotherapy

  • Chronic myelogenous leukemia (type of cancer that develops in the bone marrow, the soft tissue inside bones that helps form blood cells)

  • Infection

  • Inflammatory disorders such as Kawasaki disease (rare childhood disease that involves inflammation of the blood vessels)

  • Myelodysplasia (group of conditions in which the blood cells are abnormal in development or function)

  • Myelofibrosis (disorder that results in scar tissue in the bone marrow)

  • Polycythemia vera (rare bone marrow disorder causing excessive production of blood cells)

  • Reaction to certain medications, including steroids

  • Splenectomy (surgical removal of the spleen)

Questions for diagnosing the cause of high platelets

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your high platelets including:

  • Are you experiencing any other symptoms, such as weakness or bleeding?

  • What medications are you taking?

  • Have you been diagnosed with any other conditions?

What are the potential complications of high platelets?

Because high platelets can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan you and your health care professional design specifically for you to reduce the risk of potential complications. Potential complications of high platelets may include:

  • Bleeding

  • Blood clots

  • Brain damage such as stroke

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 2
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. What are thrombocythemia and thrombocytosis? National Heart, Lung, and Blood Institute Diseases and Conditions Index. http://www.nhlbi.nih.gov/health/dci/Diseases/thrm/thrm_what.html
  2. Primary thrombocythemia. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/000543.htm
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