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What causes a low platelet count?

Lauren Frame December 06, 2021

Platelets (also known as thrombocytes) are the part of your blood that helps it clot and stop bleeding. Without an adequate supply of this necessary blood component, there is little to keep ruptured blood vessels from stopping blood loss. Platelet donations help cancer, trauma and surgery patients recover and are always needed by area hospitals. 

What causes low platelet count?

Many factors can lead to a below-count platelet level – a condition is known as thrombocytopenia

A normal platelet count ranges from 150,000 to 400,000 per microliter of blood. A count lower than 150,000 is considered thrombocytopenia and may affect your ability to donate platelets, among other things.

A platelet count below 10,000 is considered severe thrombocytopenia. When your platelet count gets too low, it can cause dangerous internal bleeding.

Thrombocytopenia can be an inherited condition, or it can be caused by medications or other medical conditions. The platelet count in your bloodstream is reduced by one or more of the following main processes:

  1. Decreased production of platelets.
  2. Increased destruction of platelets.
  3. Increased trapping of platelets in the spleen.

What are platelets used for? Learn more on the blog.

Decreased production of platelets

Because platelets are produced in your bone marrow, decreased platelet production is often related to a bone marrow problem. Some factors that can cause decreased platelet production are:

  • Leukemia or lymphoma
  • Certain types of anemia
  • Viral infections (chickenpox, hepatitis C, HIV, etc.)
  • Chemotherapy drugs
  • Heavy alcohol consumption

Increased breakdown of platelets

Certain conditions and medications can cause your body to rapidly destroy or use up platelets faster than they are produced, leading to a shortage of platelets in your bloodstream.

These conditions include:


Low platelet count caused by pregnancy is typically mild. It usually improves soon after childbirth.

Immune thrombocytopenia

Autoimmune diseases like lupus or rheumatoid arthritis can cause the body to attack and destroy its own platelets.

Thrombotic thrombocytopenic purpura

This rare blood disorder causes small blood clots to form throughout your body. The increased clotting uses up platelets.

Hemolytic uremic syndrome

This condition affects your blood and blood vessels and results in the destruction of platelets and red blood cells, and can cause kidney failure.

Bacteria in the blood

Severe infections of the blood can lead to the destruction of platelets.


Medications like heparin, quinine and anti-seizure drugs can reduce your platelet count. Sometimes drugs confuse the immune system and cause it to destroy platelets.

Increased trapping of platelets in the spleen

The spleen is a purple, fist-shaped organ on the left side of your abdomen, just below your rib cage. It varies in size and shape but is typically about 4 inches long.

The spleen acts as a filter for your blood and helps fight bacteria. It recycles old red blood cells, and stores platelets and white blood cells.

When your spleen becomes enlarged due to advanced liver disease or blood cancers, it can hold on to an excessive number of platelets, decreasing the number in circulation throughout your body.

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Lauren Frame

Lauren Frame is a Graphic Designer at OneBlood. She has a passion for motivating and educating blood donors through storytelling.

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