Factor IX Activity

Coagulation factor tests are blood tests that check one or more of your clotting factors.

Your liver makes most of your clotting factors. But normally, clotting factors are turned off, so you don't form abnormal blood clots. When you have an injury that causes bleeding, blood cells called platelets become stickier, so they can stick to each other to make a clot and stop the bleeding.

The platelets release molecules into your blood that begin to turn on the clotting factors. The clotting factors work together in a chain reaction to form a blood clot that will stay firmly in place.

Factor IX is one of the clotting factors. It needs vitamin K to work. A shortage of factor IX activity is the cause of hemophilia B (also called Christmas disease), an inherited bleeding disorder that mainly affects males. Factor IX activity can also drop in people with severe liver disease, vitamin K deficiency, or those taking warfarin (a blood thinner).

Your provider may need to order other tests to find the cause of a problem with your clotting factors.

Lower than normal factor IX activity is the main feature of hemophilia B. Levels are often grouped to describe how severe the bleeding tendency is: about 5%-50% of normal is mild, 1%-5% is moderate, and less than 1% is severe.

Acquired (not inherited) low factor IX is more common than the inherited form and can be caused by liver disease, vitamin K deficiency, warfarin therapy, or rarely an antibody (inhibitor) against factor IX.

Higher than normal levels of one or more clotting factors may mean you have a disorder that makes your blood clot more than it should. Your provider may recommend medicine and heart-healthy lifestyle changes to help prevent clots.

Talk with your provider to find out what your tests results mean and what treatment is best for you.