Complete Blood Count (CBC)

Platelet count / Platelets

Optimal Result: 150 - 450 µl, 150.00 - 450.00 x10^9/L, or 150.00 - 450.00 x10/9/l.

Other names: Platelets, Thrombocyte Count

What are platelets?

Platelets (aka thrombocytes) are small, colorless cell fragments in our blood that form clots and stop or prevent bleeding. 

Where are platelets made?

Platelets are made in our bone marrow, the sponge-like tissue inside our bones. Bone marrow contains stem cells that develop into red blood cells, white blood cells, and platelets.

What is the main function of platelets?

Platelets form clots when there’s damage to a blood vessel. For example, if you cut your finger, platelets mix with coagulation factors/clotting factors (proteins in the blood). Together, they form a “glue” that stops the bleeding.

What is a platelet count?

A platelet count is a quick and common lab test to measure how many platelets you have in your blood.

What is a normal platelet count?

A normal platelet count is about 150,000 to 450,000 platelets per microliter of blood. There are tens of thousands of platelets in a single drop of blood.

--> Normal platelet count range: Between 150,000 and 450,000 platelets per microliter.

--> Low platelet count: Less than 150,000 platelets per microliter.

--> High platelet count: More than 450,000 platelets per microliter.

Why is it important to test your platelets?

Too few platelets can be a sign of cancer, infections or other health problems. Too many platelets put you at risk for blood clots or stroke.

When is a platelet count ordered?

A platelet count is usually part of a complete blood count (CBC). This test measures the number of platelets, white blood cells and red blood cells. The bone marrow makes blood cells.

Your healthcare provider may order a platelet count during a routine physical examination. Or they may do the test if they think you have:

- Thrombocytopenia (low platelet count).

- Thrombocytosis (high platelet count).


Ashorobi D, Gohari P. Essential Thrombocytosis. ( [Updated 2022 Jun 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan

Genetic and Rare Diseases Information Center. Essential Thrombocythemia. (

Genetic Home Reference. Essential Thrombocythemia. ( 

Lee H, Reagan JL. Thrombocytosis. In: Ferri FF, ed. Ferri’s Clinical Advisor. New York: Elsevier; 2022: 1473-1474.

National Heart, Lung, and Blood Institute. Thrombocythemia and Thrombocytosis. (

What does it mean if your Platelet count / Platelets result is too low?

A low platelet count is known as thrombocytopenia. Thrombocytopenia can occur as a result of a separate disorder, such as leukemia or an immune system problem. Or it can be a side effect of taking certain medications.


Thrombocytopenia may be mild and cause few signs or symptoms. In rare cases, the number of platelets may be so low that dangerous internal bleeding occurs. Treatment options are available.

Thrombocytopenia signs and symptoms may include:

Easy or excessive bruising (purpura):

Purpura, also called blood spots or skin hemorrhages, refers to purple-colored spots that are most recognizable on the skin. The spots may also appear on organs or mucous membranes, including the membranes on the inside of the mouth.


Superficial bleeding into the skin that appears as a rash of pinpoint-sized reddish-purple spots (petechiae), usually on the lower legs. Petechiae are tiny purple, red, or brown spots on the skin. They usually appear on your arms, legs, stomach, and buttocks. You might also find them inside your mouth or on your eyelids.

Prolonged bleeding from cuts

Bleeding from your gums or nose

Blood in urine or stools

Unusually heavy menstrual flows


Enlarged spleen


In jaundice, the skin and whites of the eyes look yellow. Jaundice occurs when there is too much bilirubin (a yellow pigment) in the blood—a condition called hyperbilirubinemia.


Thrombocytopenia can be inherited or it may be caused by a number of medications or conditions. Whatever the cause, circulating platelets are reduced by one or more of the following processes:

1. Trapped platelets

The spleen is a small organ about the size of your fist located just below your rib cage on the left side of your abdomen. Normally, your spleen works to fight infection and filter unwanted material from your blood. An enlarged spleen — which can be caused by a number of disorders — may harbor too many platelets, causing a decrease in the number of platelets in circulation.

2. Decreased production of platelets

Platelets are produced in your bone marrow. If production is low, you may develop thrombocytopenia.

Factors that can decrease platelet production include:

- Leukemia

- Some types of anemia

- Viral infections, such as hepatitis C or HIV

- Chemotherapy drugs

- Heavy alcohol consumption

3. Increased breakdown of platelets

Some conditions can cause your body to use up or destroy platelets more rapidly than they’re produced. This leads to a shortage of platelets in your bloodstream.

Examples of such conditions include:

- Pregnancy. Thrombocytopenia caused by pregnancy is usually mild and improves soon after childbirth.

- Immune thrombocytopenia. This type is caused by autoimmune diseases, such as lupus and rheumatoid arthritis. The body’s immune system mistakenly attacks and destroys platelets. If the exact cause of this condition isn’t known, it’s called idiopathic thrombocytopenic purpura. This type more often affects children.

- Bacteria in the blood. Severe bacterial infections involving the blood (bacteremia) may lead to destruction of platelets.

- Thrombotic thrombocytopenic purpura. This is a rare condition that occurs when small blood clots suddenly form throughout your body, using up large numbers of platelets.

- Hemolytic uremic syndrome. This rare disorder causes a sharp drop in platelets, destruction of red blood cells and impairment of kidney function. Sometimes it can occur in association with a bacterial Escherichia coli (E. coli) infection, such as may be acquired from eating raw or undercooked meat.

- Medications. Certain medications can reduce the number of platelets in your blood. Sometimes a drug confuses the immune system and causes it to destroy platelets. Examples include heparin, quinine, sulfa-containing antibiotics and anticonvulsants.


Dangerous internal bleeding can occur when your platelet count falls below 10,000 platelets per microliter. Though rare, severe thrombocytopenia can cause bleeding into the brain, which can be fatal.

When to see a doctor:

Make an appointment with your doctor if you have any warning signs that worry you. Bleeding that won’t stop is a medical emergency. Seek immediate help if you experience bleeding that can’t be controlled by the usual first-aid techniques, such as applying pressure to the area.

What are possible treatment options?

You might not need treatment if a low platelet count is not causing significant issues. Often, healthcare providers can improve platelet counts by treating the underlying cause. This approach may involve changing your medications.

Other treatments include:

Steroids: These medications may boost your platelet production.

Blood transfusions: If your platelet level is very low, your healthcare provider may use blood transfusions to temporarily increase your platelet levels. Transfusions may boost levels for about three days.

Splenectomy: This is surgery to remove your spleen. Your surgeon may do this if tests show your spleen is trapping large numbers of platelets. People who have splenectomies have an increased risk of developing infections. They may receive vaccinations to prevent infections.

What does it mean if your Platelet count / Platelets result is too high?

What are thrombocythemia and thrombocytosis?

Thrombocythemia and thrombocytosis are conditions that occur when your blood has a higher-than-normal platelet count.

Platelets are tiny blood cells. They are made in your bone marrow along with other kinds of blood cells. When you are injured, platelets stick together to form a plug that seals your wound. This plug is called a blood clot. Platelets are also called thrombocytes,because a blood clot is also called a thrombus. If your platelet count is too high, blood clots can form in your blood vessels. This can block blood flow through your body.

Thrombocythemia refers to a high platelet count that is not caused by another health condition. This condition is sometimes called primary or essential thrombocythemia. This is a blood and bone marrow disease.

Thrombocytosis refers to a high platelet count caused by another disease or condition. This condition is often called secondary or reactive thrombocytosis. Thrombocytosis is more common than thrombocythemia.

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.

What are symptoms of high platelet level?

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.

What causes of thrombocytosis:

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.


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.

What are the symptoms?

Many people who have thrombocythemia or thrombocytosis do not have symptoms. These conditions might be discovered only after routine blood tests. The symptoms of a high platelet count are linked to blood clots and bleeding. These symptoms are more common in people who have thrombocythemia.

Blood clots:

In thrombocythemia, blood clots most often develop in the brain, hands, and feet. But the clots can develop anywhere in the body. Blood clots in the brain may cause chronic (long-term) headaches and dizziness. In extreme cases, you may have a transient ischemic attack or a stroke. You may have blood clots in the tiny blood vessels of your hands and feet. This can make your hands and feet numb and red. You may have a burning feeling and throbbing pain, mostly in the palms of the hands and the soles of your feet.

Other symptoms of a blood clot are:

- Confusion or changes in speech

- Migraines

- Seizures

- Upper body discomfort in one or both arms, your back, neck, jaw, or abdomen

- Shortness of breath and nausea (feeling sick to your stomach)

- Weakness

- Chest pain

- Pregnancy complications

You may also have a spleen that is larger than normal.

You may have a higher chance of a blood clot if you are older, have had blood clots in the past, smoke, or have other health conditions, such as diabetes and high blood pressure.


Bleeding can happen in people who have a very high platelet count. You may have nosebleeds, bruising, bleeding from your mouth or gums, or blood in your stool.

Bleeding occurs when blood clots that develop in thrombocythemia or thrombocytosis use up your body’s platelets. This means that not enough platelets are left in your bloodstream to seal off cuts or breaks on the blood vessel walls. Bleeding can also happen if your platelets do not work properly.

Another cause of bleeding in people who have very high platelets counts is a condition called von Willebrand disease. Von Willebrand disease (VWD) is a blood disorder in which the blood does not clot properly. Blood contains many proteins that help the blood clot when needed. One of these proteins is called von Willebrand factor (VWF).

How are thrombocythemia and thrombocytosis diagnosed?

To diagnose thrombocythemia and thrombocytosis your health care professiona will ask about your medical and family history. They will ask about your symptoms and do a physical exam to look for signs of blood clots or bleeding.

Your provider may also order one or more of the tests below.

- Complete blood count (CBC): A complete blood count (CBC) measures the levels of red blood cells, white blood cells, and platelets in your blood.

- Blood smear: For this test, some of your blood is put on a slide. A microscope is used to look at your platelets and other blood cells.

- Bone marrow tests: These tests check whether your bone marrow is healthy.

- Genetic testing: This test checks for mutations, or changes, in genes that control how your body makes platelets.

What causes thrombocythemia?

Thrombocythemia occurs when faulty cells in your bone marrow make too many platelets. Your platelets also do not work properly. Bone marrow is the sponge-like tissue inside the bones. It contains stem cells that develop into platelets and other blood cells. With primary thrombocythemia, a high platelet count may happen alone or with other blood cell disorders. This condition is not common.

Thrombocythemia is most often caused by your genes. Mutations, or changes, in the genes that control how your bone marrow forms platelets may cause thrombocythemia. Examples of such genes include JAK2, CALR, and MPL. Thrombocythemia can be inherited. This means the condition can be passed from parents to children.

Primary thrombocythemia is more common in people ages 50 to 70, but it can occur at any age. It is more common in women than in men.

What causes thrombocytosis?

Thrombocytosis occurs when another disease or condition causes you to have a high platelet count. People who have thrombocytosis have normal platelets and a lower risk of blood clots and bleeding than people who have thrombocythemia. Thrombocytosis is more common than thrombocythemia.

Some conditions that can raise your risk of thrombocytosis are listed below.

Anemia: Iron-deficiency anemia and hemolytic anemia can cause thrombocytosis.

Cancer: Many people who have high platelet counts also have cancer — mostly lung, gastrointestinal, breast, or ovarian cancer or lymphoma. Sometimes a high platelet count is the first sign of cancer.

Surgery to remove your spleen: The spleen is an organ in your upper left abdomen. Normally, your spleen stores platelets. Removing your spleen can raise your platelet count.

Inflammation or infections: Conditions such as connective tissue disorders, inflammatory bowel disease, and tuberculosis can raise your platelet count.

Your platelet count may be high for only a short time. This can be caused by:

- Recovery from serious blood loss

- Recovery from a very low platelet count caused by drinking too much alcohol and having low levels of vitamin B12 or folate

- Acute (short-term) infection or inflammation

How are thrombocythemia and thrombocytosis treated?

People who have thrombocythemia with no symptoms often do not need any treatment. Other people who have this condition may need medicines or procedures to treat it. Treatment does not cure your condition, but it can help prevent blood clots and serious complications.

Treatment for secondary thrombocytosis depends on its cause. People who have thrombocytosis usually do not need platelet-lowering medicines or procedures. This is because their platelets are usually normal and less likely to cause serious blood clots or bleeding.

Treatment for thrombocythemia may include medicines and procedures.

You may need one of the following medicines to lower your platelet count:

Anagrelide: This medicine is used to lower platelet counts. It is mostly used when hydroxyurea does not work. Anagrelide also has side effects, such as fluid retention, palpitations, arrhythmias, heart failure, and headaches.

Aspirin: This medicine helps prevent blood clots. It is mostly used in people who have a low risk of blood clots. If you have a high risk of blood clots, you may need to take both aspirin and hydroxyurea.

Hydroxyurea: This platelet-lowering medicine is used to treat cancers and sickle cell disease, for example.

Interferon alfa: This medicine lowers platelet counts, but it can have serious side effects. Side effects may include a flu-like feeling, decreased appetite, nausea (feeling sick to the stomach), diarrhea, seizures, irritability, and sleepiness.


Plateletpheresis is a procedure used to quickly lower your platelet count. This procedure is mostly used for emergencies. For example, if you are having a stroke due to primary thrombocythemia, you may need plateletpheresis.

An intravenous (IV) needle that is connected to a tube is placed in one of your blood vessels to remove blood. The blood goes through a machine that removes platelets from the blood. The remaining blood is then put back into you through an IV line in one of your blood vessels.

What health problems can thrombocythemia and thrombocytosis cause?

Thrombocythemia and thrombocytosis may cause blood clots which can block blood flow to your organs. This can lead to the following serious complications:

- Venous thromboembolism
- Stroke and transient ischemic attacks
- Reduced blood flow to your heart, which can cause a heart attack
- Pregnancy complications

Thrombocytopenia and thrombocytosis can also cause your bone marrow to become scarred or to produce too many blood cells. This may lead to some types of leukemia.

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