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Quick Facts

High Platelet Count

(Thrombocythemia)

By

The Manual's Editorial Staff

Last full review/revision Jun 2020| Content last modified Jun 2020
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Platelets are tiny cells in your blood that help your blood clot. A high platelet count can cause problems with blood clotting.

  • Sometimes your body makes too many platelets

  • You might develop clots in your blood vessels or have unusual bleeding

  • Your hands and feet may burn and tingle

  • Doctors do blood tests to see why you have too many platelets and sometimes take a small sample of your bone marrow

  • Doctors will give you medicines to ease your symptoms and lower the platelet count

What causes a high platelet count?

Your body makes platelets and other blood cells, such as red blood cells and white blood cells, in your bone marrow. The marrow is the soft material in the center of your bones. Platelets come from the same blood-forming cells that make other blood cells.

A high platelet count can be caused by:

  • A problem with blood-forming cells

  • A reaction to a disease

Sometimes blood-forming cells just make too many platelets. This is usually because there's a problem with one of the genes that control the making of platelets. This problem usually happens after about age 50, but sometimes it happens to young women. Less often, the problem involves genes that also control other blood cells. This can result in a more serious blood disorder.

Often, a high platelet count is a reaction to a disease such as certain cancers, infections, or immune system problems.

What are the complications of a high platelet count?

Some people don't have any complications. But if you do, there are two main types:

  • Too much blood clotting

  • Too much bleeding

Too much clotting and too much bleeding seem like opposites. But both can result from having too many platelets.

Too much clotting

At first, having too many platelets makes your blood more likely to clot—clotting is the job of platelets. You may get clots in your legs (DVT), in your brain (stroke), or in your lungs (pulmonary embolism).

Too much bleeding

When your platelet count is extremely high, the extra platelets actually interfere with blood clotting. Your blood vessels may leak blood on their own or after only a minor injury.

What are the symptoms of a high platelet count?

A high platelet count itself often doesn't cause any symptoms. But you may feel:

  • Burning or tingling in your fingertips, hands, and feet

  • Headaches

  • Weak, dizzy, and tired

Symptoms of abnormal blood clots include:

  • A painful, swollen leg

  • Chest pain and shortness of breath

  • Weakness of one side of your body

Symptoms of excessive bleeding include:

  • Nosebleeds

  • Bleeding gums

  • Easy bruising

How can doctors tell if I have a high platelet count?

Platelets are measured as part of a standard test called a complete blood count (CBC). To see why your platelets are high, doctors may do other blood tests, including special genetic tests. They also may need to take a small sample (biopsy) of your bone marrow and examine it under a microscope.

How do doctors treat a high platelet count?

Doctors will treat any medical problem that has caused your high platelet count. When that problem gets better, your platelet count should go down.

Doctors may give you small doses of aspirin to help ease mild symptoms. You'll likely be admitted to the hospital if you have a lot of bleeding, or if you have a heart attack or stroke because of clots caused by the high platelet count.

Doctors may try to lower the amount of platelets in your blood with:

  • Medicine

  • Platelet exchange—doctors remove some blood, take platelets out of it, then return the blood to your body

  • Rarely, stem cell transplantation if you're young, have a donor, and other treatments have been unsuccessful

You'll need blood tests every so often to make sure that your platelet count hasn't gone back up.

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