A fibrinogen activity test is also known as a Factor I assay. It’s used to determine the level of fibrinogen in your blood. Fibrinogen, or factor I, is a blood plasma protein that’s made in the liver. Fibrinogen is one of 13 coagulation factors responsible for normal blood clotting.
When you start to bleed, your body initiates a process called the coagulation cascade, or clotting cascade. This process causes coagulation factors to combine and produce a clot that will stop the bleeding. If you don’t have enough fibrinogen or if the cascade isn’t working normally, clots will have difficulty forming. This can cause excessive bleeding.
Fibrinogen is measured in milligrams per deciliter (mg/dL):
- A normal value for fibrinogen is between 200 and 400 mg/dL.
- A fibrinogen value of less than 50 mg/dL may mean you're in danger of bleeding after surgery.
- A fibrinogen value of more than 700 mg/dl may mean you're in danger of forming clots that could harm your heart or brain.
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