Blood clotting tests are used to diagnose and assess bleeding problems, and to monitor people who take warfarin or other anticoagulant medicines.

Some conditions can prevent blood from clotting properly, may cause the blood to clot too easily or cause clots to remain in the body too long.

Coagulation tests can be used to monitor patients taking anticoagulants (medications that decrease the ability of the blood to clot).

Anticoagulant medications are often prescribed to patients after they have suffered a heart attack or stroke. Those with arrhythmia (irregular heart beats) may also take anticoagulants to prevent a first or recurrent stroke.

Coagulation tests may also be used to evaluate a patient’s risk of excessive bleeding before surgery. These type of tests are called Pre-Operative tests. See our range of pre-operative tests under 'P' of the A-Z of tests.

There are many types of coagulation tests. Some are general and tell only whether or not a person’s blood is clotting normally. Other tests can identify which element within the blood is causing abnormal clotting. There are also tests to measure how well the body destroys blood clots that are no longer needed.

Prothrombin Time measures the time it takes for blood to clot. Blood clotting requires vitamin K and a protein made by the liver. Liver cell damage and bile flow obstruction can both interfere with proper blood clotting. An equivalent measure sometimes used is the Kaolin Cephalin Clotting Time (KCCT).

Thrombin Time measures the amount of time it takes blood to clot when thrombin is added to a sample of blood. If blood does not clot immediately, a fibrinogen deficiency is present. If a patient is receiving heparin, a substance called reptilase derived from snake venom is used to substitute for the thrombin time test. The thrombin time is used to diagnose bleeding disorders and to assess the effectiveness of fibrinolytic therapy.