Fibrinogen
Fibrinogen (coagulation factor I) is a protein made by the liver that is converted to fibrin strands during clotting. It is both a clotting factor and an acute-phase reactant — levels rise in inflammation, infection, pregnancy, and after surgery. Fibrinogen is used to assess bleeding risk in liver disease, DIC, and massive transfusion protocols, and as an inflammation marker.
Reference Ranges
Male
200 – 400
mg/dL
Female
200 – 400
mg/dL
Child
150 – 400
mg/dL
Ages 1–12
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low fibrinogen (below 150–200 mg/dL) raises bleeding risk. Causes include advanced liver disease, DIC, massive transfusion with dilutional loss, congenital afibrinogenemia, and asparaginase chemotherapy. Replacement with cryoprecipitate or fibrinogen concentrate may be needed before surgery or during active bleeding.
What High Levels Mean
Elevated fibrinogen (above 400 mg/dL) is seen in any acute-phase response — infection, inflammation, trauma, pregnancy, and malignancy. Chronic elevation is an independent cardiovascular risk factor, reflecting both inflammation and a pro-thrombotic state. Levels above 700 mg/dL are substantial and warrant evaluation.
Frequently Asked Questions
Why is fibrinogen measured before surgery?
Fibrinogen is the first clotting factor to become depleted in major bleeding. Preoperative fibrinogen below 200 mg/dL predicts higher blood transfusion requirements. It is particularly important in cardiac surgery, postpartum hemorrhage, and trauma resuscitation.
Is high fibrinogen dangerous?
Chronically elevated fibrinogen is associated with higher risk of heart attack, stroke, and venous thromboembolism. It also reflects underlying inflammation — the key question is why it is high. Addressing the underlying cause (treating infection, reducing cardiovascular risk factors, controlling chronic inflammation) matters more than fibrinogen itself.
How is fibrinogen different from D-dimer?
Fibrinogen is the intact precursor protein; D-dimer is a breakdown fragment produced after a clot has formed and been dissolved. In DIC both are abnormal — fibrinogen drops as it is consumed, and D-dimer rises as clots are broken down. Together they form the core of the DIC panel.
Related Coagulation tests
See all →D-Dimer
Fragment released when a blood clot breaks down.
µg/mL FEUCoagulationProthrombin Time / INR (PT/INR)
Measures how long blood takes to clot via the extrinsic pathway.
INRCoagulationActivated Partial Thromboplastin Time (aPTT)
Measures clotting via the intrinsic pathway — used for heparin monitoring.
secondsThis information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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