Skip to Content

Overview of Blood Clotting Disorders

By

Joel L. Moake

, MD, Baylor College of Medicine

Last full review/revision Jan 2020| Content last modified Jan 2020

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

  • Too little clotting, leading to abnormal bleeding (hemorrhage)
  • Too much clotting, leading to the development of blood clots (thrombosis)

Abnormal bleeding means that people bruise and bleed too easily (see also Bruising and Bleeding and How Blood Clots). Abnormal bleeding can result from disorders of

  • Blood clotting (coagulation) system
  • Platelets
  • Blood vessels

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.

Sometimes there is an abnormality of blood coagulation that increases the risk of clotting (called thrombophilia).

Disorders of coagulation can be

  • Hereditary
  • The result of some other disorder

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. 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.

Copyright © 2022 Merck & Co., Inc., known as MSD outside of the US, Kenilworth, New Jersey, USA. All rights reserved. Merck Manual Disclaimer