Fibrinogen Resist Since 1996, Life Extension has warned about the lethal dangers of excess fibrinogen, an inflammatory protein produced by the liver. Studies appearing in the world"s most prestigious medical journals indicate that excess fibrinogen is a strong predictive mortality factor. According to one study, "fibrinogen levels were the only independent predictor of mortality."1 Life Extension has reviewed dozens of studies and determined that optimal fibrinogen levels should range between 215 and 300 milligrams per deciliter (mg/dL) of blood