Does this test have other names?

Platelet count, thrombocyte count

What is this test?

This test measures the number of platelet cells in your blood.

Platelets are disk-shaped cells that help your blood form clots. Platelets are also called thrombocytes. They are made in the spongy center of bones, called the bone marrow. About two-thirds of your platelets circulate in your blood all the time. They live for about 7 days.

The number of platelets in your blood can give your healthcare provider valuable information about how well your blood clots to stop bleeding, how well your bone marrow is working, and about diseases that affect your platelet count.

Why do I need this test?

You may need this test if you are having routine blood testing during a physical exam. You may also need this blood test if you have signs or symptoms that you may have too many or too few platelets.

Having too many platelets is called thrombocythemia or thrombocytosis. Symptoms may include:

• Weakness

• Bleeding

• Headache and dizziness

• Numbness and burning of hands and feet

Having too few platelets is called thrombocytopenia. Symptoms may include:

• Red or brown bruising of the skin, a condition called purpura

• Small red dots on the skin, a condition called petechiae

• Nosebleeds

• Mouth bleeding

• Blood in bowel movements

• Heavy or prolonged menstrual periods

You may also have this test if a blood test called a peripheral smear shows an abnormal platelet count.

What other tests might I have along with this test?

Your healthcare provider may also order a complete blood count (CBC), which measures all the cells in your blood.

Your provider may also order a mean platelet volume (MPV). MPV tells your provider about the size of your platelets. You may also need blood tests to look at your blood's ability to form blood clots. This is called a coagulation profile.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

Platelets are measured as the number of platelets found in 1 microliter of blood. This is what the numbers may mean:

• 150,000 to 450,000 platelets is normal

• Fewer than 150,000 platelets is low

• Fewer than 50,000 may cause mild bleeding

• Fewer than 20,000 may cause serious bleeding

Some common causes of an abnormally high number of platelets include:

• Blood cell cancers such as leukemia, lymphoma, and Hodgkin disease

• Other cancers

• Kidney failure

• Inflammatory disease such as rheumatoid arthritis

• Certain types of anemia

• Active infections

Some common causes of an abnormally low number of platelets include:

• Certain types of anemia

• Infections

• Heart failure

• Cancer treatment

• Bone marrow cancers

• Alcohol abuse

• Bleeding

• Certain inherited syndromes

• Liver or kidney disease

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What might affect my test results?

Your platelet count may go up if you live at a high altitude or have recently exercised strenuously. Your platelet count may go down if you are about to have a menstrual period, are pregnant, or are taking birth control pills.

Certain medicines can also affect your platelet count.

How do I get ready for this test?

You should avoid strenuous exercise before the test. If you are a woman, let your healthcare provider know if you may be pregnant or are having your period. Be sure your provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.