Merck Manual

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Overview of Blood Clotting Disorders

By

Michael B. Streiff

, MD, Johns Hopkins University School of Medicine

Reviewed/Revised Sep 2023
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Topic Resources

Blood clots help stop bleeding. Blood clotting (coagulation) disorders are dysfunctions in the body's ability to control the formation of blood clots. These dysfunctions may result in

Clotting disorders occur when the body is unable to make sufficient amounts of the proteins that are needed to help the blood clot, stopping bleeding. These proteins are called clotting factors (coagulation factors). All clotting factors are made in the liver. The liver requires vitamin K to make some of the clotting factors.

Disorders of coagulation can be

  • Hereditary

  • The result of some other disorder

Disorders of coagulation also occasionally develop on their own (spontaneously).

The most common hereditary coagulation disorders are

The primary causes of coagulation disorders that develop as a result of another disorder are

Tests of Blood Clotting

One commonly tested measure that affects the body's ability to stop bleeding is the count of the number of platelets Platelets The main components of blood include Plasma Red blood cells White blood cells Platelets read more Platelets . Less often, doctors test how well the platelets function.

Other tests can measure the overall, coordinated function of the many proteins needed for normal blood clotting (clotting factors). The most common of these tests are the prothrombin time (PT) and the partial thromboplastin time (PTT).

The levels of individual clotting factors can also be determined.

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