Blood-Clotting Disorders

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Topic Overview

Some people are born with an increased tendency to form blood clots. These are called inherited blood-clotting disorders. They are often related to:

  • Mutated genes (such as factor V Leiden, factor II).
  • Decreased amounts of certain proteins. These may include protein C, protein S, and antithrombin III.
  • Increased levels of other substances. These may include antiphospholipid and lupus anticoagulant.

Other people get blood clots because of a health problem. Blood clots can happen after surgery or injury. And they can happen when a person doesn't move around for a long time.

Blood clots can be especially serious when they are in the legs ( deep vein thrombosis ) and in the lungs ( pulmonary embolism ).


There are several tests that can help find the cause of a blood clotting problem. Talk to your doctor about whether you need testing.

These tests may include:

  • Fibrinogen.
  • Antithrombin.
  • Protein C.
  • Protein S.
  • Factor V Leiden.
  • Antiphospholipid antibody
  • Lupus anticoagulant.

Related Information


Other Works Consulted

  • Lipe B, Ornstein DL (2011). Deficiencies of natural anticoagulants, protein C, protein S, and antithrombin. Circulation, 124(14): e365–e368.


ByHealthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Jeffrey S. Ginsberg, MD - Hematology

Current as ofFebruary 9, 2015