Also known as: Clottable Fibrinogen, Factor I Activity.

Fibrinogen is produced by the liver and released into the circulation as necessary along with over 20 other clotting factors. Usually, when a body tissue or blood vessel wall is injured, the coagulation cascade activates these clotting factors one after the other. As this cascade nears completion, soluble fibrinogen is changed into insoluble fibrin threads. The threads then crosslink together to form a fibrin net that stabilizes at the injury site. The fibrin net will adhere to the site of injury along with platelets to form a stable blood clot. This barrier will prevent additional blood loss and will remain in place until the injured area has healed. Fibrinogen is one of several blood factors called acute phase reactants. Blood levels of fibrinogen along with other acute phase reactants will rise sharply with conditions causing acute tissue inflammation or damage. Fibrinogen testing measures the amount of soluble Factor I, which is fibrinogen dissolved in the blood, before it has been turned into insoluble fibrin and been crosslinked into a fibrin net.