Medical knowledge, Patient Education
Activated Clotting Time Test
Why am I having this test?
An activated clotting time (ACT) test is used to measure how long it takes for your blood to clot. This test is done to monitor the blood-thinning (anticoagulant) effect of blood thinners, such as heparin or other medicines, during some medical procedures.
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Take over the work of the heart during surgery (cardiopulmonary bypass, or CPB).
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Open clogged arteries using a balloon (cardiac angioplasty).
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Clean the blood when the kidneys have stopped working (hemodialysis).
What is being tested?
An ACT test measures the time it takes for whole blood to clot.
What kind of sample is taken?
A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel. This type of blood test must be performed immediately after the blood is collected, close to the person being tested. It is usually done at the bedside or in the operating room.
How are the results reported?
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Therapeutic range for anticoagulation: 150–600 seconds. This refers to the target time by which a person’s blood should clot if he or she is taking heparin or other blood-thinning medicines.
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Normal range: 70–120 seconds. This is the normal time that blood takes to clot without any heparin or other blood-thinning medicines.
What do the results mean?
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Increased ACT can be seen if you:
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Are receiving heparin or the blood thinner called warfarin.
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Have certain clotting factor deficiencies.
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Have cirrhosis of the liver.
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Have certain antibodies that act against components involved in the clotting process (lupus inhibitors).
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Decreased ACT can be seen if you have blood clots (thrombosis).
Talk with your health care provider about what your results mean.
Questions to ask your health care provider
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When will my results be ready?
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How will I get my results?
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What are my treatment options?
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What other tests do I need?
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What are my next steps?
Summary
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An activated clotting time (ACT) test is used to measure how long it takes for your blood to clot.
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This test is done to monitor the blood-thinning (anticoagulant) effect of blood thinners, such as heparin or other medicines, during some medical procedures.
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This test may be used during procedures that are done to open clogged arteries (cardiac angioplasty), clean the blood (hemodialysis), or take over the work of the heart during surgery (cardiopulmonary bypass).
This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.
