Fibrinogen is a blood fraction that is essential for clotting. It is decreased in two ways, both relatively uncommon: (1) by intravascular deposition of fibrin in the form of small clots (DIC) and (2) by inactivation in the presence of primary fibrinolysin. Fibrinogen concentrates used to be prepared commercially but are no longer available due to the considerable risk of hepatitis. Cryoprecipitate contains 150 mg or more of fibrinogen per bag and is the most commonly used source of therapeutic fibrinogen.