Fibrinogen is the plasma protein the liver makes as the final substrate of clotting, converted into fibrin to form the clot itself. It is also an acute-phase reactant, so its concentration rises as part of the general inflammatory response. The result therefore speaks both for coagulation capacity and for the liver that produces it.
No readings for this marker yet.
Higher values most often reflect ongoing inflammation, infection, tissue injury, pregnancy or smoking, and persistently high levels are also treated as a cardiovascular risk marker. Lower values most often point at reduced production in advanced liver disease, at consumption during heavy bleeding or disseminated intravascular coagulation, or at a rare inherited deficiency. Either direction is a finding to repeat and to bring to a doctor, not a diagnosis.
The sample requires a correctly filled citrate tube, since an under-filled or clotted tube distorts the result; recent inflammation, pregnancy, oral contraceptives and anticoagulant or thrombolytic treatment all shift it. It is read alongside C-reactive protein and the sedimentation rate when the question is inflammation, and alongside the clotting times and platelet count when the question is bleeding.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.