Thrombocytopenia (Low Platelet Count)

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Author: Siamak N. Nabili, MD, MPH
    Siamak N. Nabili, MD, MPH

    Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Take the Blood Disorders Quiz

What is thrombocytopenia (low platelet count)?

Thrombocytopenia is a lower than normal number of platelets (less than 150,000 platelets per microliter) in the blood. Normal platelet counts range from 150,000 to 400,000 per microliter in the blood.

Platelets are one of the cellular components of the blood along with white and red blood cells. Platelets play an important role in clotting and bleeding. Platelets are made in the bone marrow similar to other cells in the blood. Platelets originate from megakaryocytes which are large cells found in the bone marrow. The fragments of these megakaryocytes are platelets that are released into the blood stream. The circulating platelets make up about two third of the platelets that are released from the bone marrow. The other one third is typically stored (sequestered) in the spleen.

Platelets, in general, have a brief lifespan in the blood (7 to 10 days), after which they are removed from circulation. The number of platelets in the blood is referred to as the platelet count and is normally between 150,000 to 400,000 per micro liter (one millionth of a liter) of blood. Platelet counts less than 150,000 are termed thrombocytopenia. A platelet count greater than 400,000 is called thrombocytosis.

Platelets participate in coagulation. Platelets initiate a sequence of reactions that eventually lead to the formation of a blood clot. They circulate in the blood vessels and become activated if there is any bleeding or injury in the body. Certain chemicals are released from the injured blood vessels or other structures that signal platelets to become activated and join the other components of the system to initiate coagulation. When activated, the platelets become sticky and adhere to one another and to the blood vessel wall at the site of the injury to slow down and stop the bleeding by plugging up the damaged blood vessel or tissue (hemostasis).

It is important to note even though the platelet numbers are decreased in thrombocytopenia, their function often remains completely intact. Other disorders exist that can cause impaired platelet function despite normal platelet count.

A platelet count below 10,000 is severe thrombocytopenia and may result in spontaneous bleeding. In mild thrombocytopenia, there may be no adverse effects in the clotting or bleeding pathways. These effects vary with different low platelet counts from person to person.

Picture of platelets and a blood clot
Picture of platelets and a blood clot
Medically Reviewed by a Doctor on 7/1/2016

Subscribe to MedicineNet's Newsletters

Get the latest health and medical information delivered direct to your inbox!

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

VIEW PATIENT COMMENTS
  • Thrombocytopenia - Describe Your Experience

    Please describe your experience with Thrombocytopenia.

    Post View 31 Comments
  • Thrombocytopenia (Low Platelet Count) - Causes

    What was the cause of your thrombocytopenia?

    Post View 5 Comments
  • Thrombocytopenia (Low Platelet Count) - Symptoms

    What were your symptoms associated with a low platelet count?

    Post View 3 Comments
  • Thrombocytopenia (Low Platelet Count) - Diagnosis

    What tests and exams did you receive that led to a diagnosis of thrombocytopenia?

    Post View 1 Comment
  • Thrombocytopenia (Low Platelet Count) - Treatment

    What kinds of treatment did you receive for thrombocytopenia?

    Post View 4 Comments

Health Solutions From Our Sponsors