by EBSCO Medical Review Board
(HIT; Heparin-induced Low Blood Platelet Count)


Thrombocytopenia means low blood platelet count. These are a special type of blood cell. They help form clots so that you do not bleed too much.

Heparin is a blood thinner that lowers the risk of blood clots. Heparin-induced thrombocytopenia (HIT) is low blood platelet count caused by heparin. It can lead to too much blood clotting. Too much bleeding is rare.

Clot Formation
blood clot platelet
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HIT is caused by platelets clumping due to an immune reaction to heparin. The clumping uses them up and lowers the count.

Risk Factors

Taking heparin is a risk for having this health problem.


Symptoms are from blood vessels being blocked:

  • Pain or swelling in the legs
  • Chest pain
  • Problems breathing
  • Anxiety
  • Sweating
  • Rapid, uneven heartbeat
  • Headache


You will be asked about your symptoms and health history. An exam will be done.

Blood tests will be done to check your platelet count.


Treatment may include:

  • Stopping the use of heparin.
  • Blood thinners to lower the risk of blood clots.
  • Vitamin K antagonists (VKA) therapy—in people taking a VKA, it will be stopped and vitamin K will be given; the VKA will be started again when the person's platelet count is normal.
  • Platelet transfusion may be given to replace used up platelets if there is a lot of bleeding, but this is rare.


To lower the chance of this problem:

  • Avoid heparin use.
  • Take other blood thinners.


American Heart Association 

Family Doctor—American Academy of Family Physicians 


Canadian Cardiovascular Society 

Heart and Stroke Foundation of Canada 


Arepally GM. Heparin-induced thrombocytopenia. Blood. 2017 May 25;129(21):2864-2872.

Heparin-induced thrombocytopenia (HIT). EBSCO DynaMed website. Available at: . Updated August 30, 2018. Accessed August 14, 2019.

Heparin sodium. EBSCO Nursing Reference Center website. Available at: . Updated September 7, 2018. Accessed August 14, 2019.

Revision Information

  • Reviewer: EBSCO Medical Review BoardJames P. Cornell, MD
  • Review Date: 08/2019
  • Update Date: 12/13/2019