Version July 2025
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What are clotting factors? —
These are natural proteins found in the blood. They help the blood to clot. This is important so that the body can control bleeding if you get a cut or injury. Doctors also use the term "coagulation factors."
The body makes many different clotting factors. Each factor has a name, a Roman numeral, or both. For example:
●Factor VIII – This is factor eight (8). It is missing or very low in people with hemophilia A.
●Factor IX – This is factor nine (9). It is missing or very low in people with hemophilia B.
●Factor XI – This is factor eleven (11). It is missing or very low in people with factor XI deficiency, also called hemophilia C.
●Fibrinogen – This can be missing or very low in people with severe liver disease, hemorrhage after giving birth, severe trauma, or a condition called disseminated intravascular coagulation.
When certain clotting factors are missing or too low, this can cause dangerous bleeding.
Blood tests can check these clotting factors. There are also tests for other clotting factors, but these are not used as often.
What is a clotting factor test? —
This is a blood test to measure 1 of your clotting factors and check how well it is working. It can show if the clotting factor is missing or too low.
Less commonly, there might be enough of the factor, but it is not working as it should.
Why might I get a clotting factor test? —
Doctors can do a clotting factor test for different reasons, for example:
●If you have severe bleeding
●If you had a general blood clotting test, like a "PT/INR" or "PTT," and the results were abnormal – The PT and PTT tests measure how long it takes your blood to clot.
●If a bleeding disorder like hemophilia runs in your family
●To monitor you if you are getting treatment for a bleeding disorder like hemophilia
How do I prepare for a clotting factor test? —
For this test, you need to get a "blood draw." Your doctor or nurse will tell you where to go for this.
It might help to wear a short-sleeve shirt to your blood draw appointment. This makes it easier for the person drawing your blood to get to your arm.
What happens during a blood draw? —
For the blood draw, a needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.
Tell the person who takes your blood:
●If you have a latex allergy – Some of the supplies used for blood draws might contain latex.
●If you have a preferred arm to use
Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in. Hold pressure on the area and make sure that the bleeding stops before you leave.
What do my results mean? —
Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.
If the test shows that your clotting factor is low, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out the cause.
If you do have a health problem, your doctor will work with you to come up with a plan for treatment.
Patient education: Prothrombin time and INR (PT/INR) (The Basics)
Patient education: Partial thromboplastin time test (The Basics)
Patient education: Hemophilia (The Basics)
Patient education: von Willebrand disease (The Basics)
Patient education: Disseminated intravascular coagulation (The Basics)
Patient education: Managing increased bleeding risk (The Basics)
Patient education: von Willebrand disease (Beyond the Basics)
