Definition

Thrombocytopenia means there is an abnormally low amount of platelets. Platelets are parts of the blood that help blood to clot. This condition is sometimes associated with abnormal bleeding.

Alternative Names

Low platelet count - thrombocytopenia

Causes

Thrombocytopenia is often divided into 3 major causes of low platelets:

• Not enough platelets are made in the bone marrow
• Increased removal of platelets in the bloodstream
• Increased trapping of platelets in the spleen or liver

Your bone marrow may not make enough platelets if you have any of the following conditions:

• Aplastic anemia (disorder in which the bone marrow does not make enough blood cells)
• Cancer in the bone marrow, such as leukemia
• Cirrhosis (liver scarring)
• Folate deficiency
• Infections in the bone marrow (very rare)
• Myelodysplastic syndrome (bone marrow does not make enough blood cells or makes defective cells)
• Vitamin B12 deficiency

Use of certain medicines may also lead to a low production of platelets in the bone marrow. The most common example is chemotherapy treatment for cancer.

The following health situations cause a low number of platelets:

• Disorder in which the proteins that control blood clotting become over active, most often during a serious illness (disseminated intravascular coagulation - DIC)
• Drug-induced low platelet count
• Enlarged spleen
• Disorder in which the immune system destroys platelets (immune thrombocytopenic purpura - ITP)
• Disorder that causes blood clots to form in small blood vessels, causing a low platelet count (thrombotic thrombocytopenic purpura - TTP)

Symptoms

You may not have any symptoms. Or you may have general symptoms, such as:

• Bleeding in the mouth and gums
• Bruising
• Nosebleeds
• Rash

Other symptoms depend on the cause.

Exams and Tests

Your health care provider will perform a physical exam and ask about your medical history and symptoms. The following tests may be done:

• Complete blood count (CBC)
• Blood clotting tests: partial thromboplastin time (PTT) and prothrombin time (PT)

Other tests that may help diagnose this condition include bone marrow aspiration or biopsy.

Treatment

Treatment depends on the cause of the condition. In some cases, a transfusion of platelets may be required to stop or prevent bleeding.

Outlook (Prognosis)

The outcome depends on the disorder causing the low platelet counts.

Possible Complications

Severe bleeding (hemorrhage) is the main complication. Bleeding may occur in the brain or gastrointestinal tract.

When to Contact a Medical Professional

Contact your provider if you experience unexplained bleeding or bruising.

Prevention

Prevention depends on the specific cause.

References

Abrams CS. Thrombocytopenia. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 158.

Branchford BR, Samelson-Jones BJ, Flood VH. Platelet and blood vessel disorders. In: Kliegman RM, St. Geme JW, Blum NJ, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 533.

Warkentin TE. Thrombocytopenia caused by hypersplenism, platelet destruction, or surgery/hemodilution. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 130.

Zeller MP, Ning S, Arnold DM, Gabe C. Diseases of platelet number: immune thrombocytopenia, neonatal alloimmune thrombocytopenia, and posttransfusion purpura. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 129.