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ACT, activated clotting time
This test measures how long it takes your blood to clot. It's often used to check how well the drug heparin is working. Heparin slows the ability of blood to clot, and the ACT test helps your health care provider determine the right dosage.
You may need this test if you are getting heparin to prevent your blood from clotting during a procedure such as open heart surgery, cardiac catheterization, or kidney dialysis. This test is usually done in the hospital at your bedside.
You may have other blood tests to measure how quickly your blood clots. A blood test called activated partial thromboplastin time (APTT) is often done as a backup to the results of the ACT test.
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
This test is measured in the number of seconds it takes for a blood clot to form:
70 to 120 seconds is the usual amount of time for blood to clot without heparin.
180 to 240 seconds is the usual amount of time for blood to clot with heparin. This is called the therapeutic range.
The therapeutic range is usually about double the normal clotting time. It's important to be in this range because if your ACT is too low, you may be in danger of a blood clot forming during a procedure. Some procedures may require an even longer ACT.
If your ACT is too high, you may be in danger of bleeding.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
This test measures only how long it takes your blood to clot. It does not measure the amount of heparin in your blood.
Other factors that may affect your results include:
The effects of surgery
Other drugs you are taking
Getting intravenous fluids, which can dilute your blood
Platelet counts and platelet function
Coagulation factor deficiencies
You don't need to prepare for this test. But be sure your health care provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.
Bayhealth is Southern Delaware’s healthcare leader with hospitals in Dover and in Milford. Bayhealth provides a wide range of medical services, including cardiovascular, cancer, orthopaedics and rehabilitation, pediatrics, respiratory care, sleep care, surgical weight loss and women’s services.