Coagulation Studies

Emily Tester

What is coagulation?

When a break occurs in a blood vessel wall (from skin cuts or abrasions)- a process called coagulation occurs that leads to the formation of a blood clot, which stops the bleeding.


-Blood cells cells called platelets clump at the injury site. The injured cells and platelets both trigger the release of special substances, called clotting factors into the bloodstream.


At least a dozen blood clotting factors are needed to clot blood and stop bleeding. (Coagulation).


Coagulation tests measure your blood’s ability to clot, as well as how long it takes. Testing can help your doctor assess your risk of excessive bleeding or developing clots (thrombosis) somewhere in your blood vessels.

Why are coagulation studies used?

To see if you have a bleeding disorder.

If you are put on a blood thinner medicine, they check you.

If you have excessive bleeding and/or bruising.

To look for signs of blood clotting.

Who should get tested?

  • People on blood thinners
  • People with bleeding disorders.
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How is this procedure done?

  • You may be required to discontinue taking medications prior to the test.
  • Your healthcare provider will sterilize the top of your hand or inside your elbow.
  • A needle will be inserted into a vein. Blood will be drawn and collected.
  • Small bandage will be placed on the puncture site.
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What are some types of coagulation tests?

  • Complete Blood Count.
  • Factor V
  • Fibrinogen Level
  • Prothrombin time (PT)
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What are the normal results of the procedure?


  • PT is measured in seconds. Most of the time, results are given as what is called INR (international normalized ratio).
  • If you are not taking blood thinning medicines the normal range for your PT results is: 11 to 13.5 seconds. The INR would be around 0.8 to 1.1.
  • If you are taking medicine to prevent blood clots, your doctor will most likely choose to keep your INR between 2.0 and 3.0.
  • Normal value ranges may vary among different labs. Some labs use different measurements or different test samples.
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What are the implications of abnormal results?

If you are not taking blood thinning medicines, such as warfarin, an INR result above 1.1 means your blood is clotting more slowly than normal. This may be due to:


  • Bleeding disorders
  • Liver disease
  • Low level of vitamin K.



If you are taking medicine to prevent clots your doctor will most likely choose to keep your INR between 2.0 and 3.0.


  • Depending on why you are taking the blood thinner, the desired level may be different
  • Even when your INR stays between 2.0 and 3.0, you are more likely to have bleeding problems.
  • INR results higher than 3.0 may put you at even higher risk for bleeding.
  • INR results lower than 2.0 may put you at risk for developing a blood clot.
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