What is a normal fibrinogen level?

Normal Fibrinogen Level

Normal plasma fibrinogen concentration ranges from 2.0 to 4.0 g/L (200-400 mg/dL) in healthy individuals. 1, 2, 3

Reference Range Details

• Standard range: 1.5-4.0 g/L in healthy adults 4
• More conservative range: 2.0-4.0 g/L is most commonly cited in clinical guidelines 1, 2
• Alternative units: 150-400 mg/dL (equivalent to 1.5-4.0 g/L) 3
• Half-life: 3-5 days under normal physiological conditions 4

Clinical Context for Interpretation

Critical Thresholds for Bleeding Risk

Fibrinogen levels below 1.5-2.0 g/L indicate significant deficiency requiring intervention in bleeding scenarios. 1, 2

• <1.0 g/L: Critically low, first coagulation factor to reach dangerous levels during massive hemorrhage 1
• <1.5 g/L: Associated with impaired clot strength and increased bleeding risk 1
• <2.0 g/L: Threshold used in trauma settings for fibrinogen replacement 1

Disease-Specific Considerations

**In cirrhosis, fibrinogen levels <100 mg/dL (1.0 g/L) are associated with spontaneous and procedure-related bleeding**, though causality remains debated 1. The most commonly used threshold for fibrinogen replacement in actively bleeding cirrhotic patients is >120 mg/dL (1.2 g/L) 1.

In trauma patients without liver disease, maintaining fibrinogen >200 mg/dL (2.0 g/L) is associated with more effective hemostasis. 1

Pregnancy-Related Changes

Fibrinogen levels physiologically increase during pregnancy, which is a normal adaptive response 2. For women with congenital fibrinogen disorders during pregnancy, target trough levels should be maintained ≥1.0 g/L throughout pregnancy and ≥1.5 g/L for labor and delivery 1, 5.

Measurement Methods

The Clauss method is the most frequently recommended laboratory technique for measuring fibrinogen concentration. 1

Important Caveats

• Artificial colloids (hydroxyethyl starch) significantly overestimate fibrinogen levels when using the Clauss method 1, 2
• Prothrombin-time-derived methods systematically overestimate fibrinogen in anticoagulated patients and those with levels >400 mg/dL 6
• Viscoelastic testing (thromboelastometry/TEG) provides functional assessment of fibrinogen contribution to clot strength, which may be more clinically relevant than static plasma levels 1, 2, 7

Elevated Fibrinogen

Fibrinogen functions as an acute phase reactant and elevates during inflammatory processes, with levels above 4.0 g/L considered elevated. 2

• Increases alongside C-reactive protein during inflammation 2
• Associated with cardiovascular risk, particularly in acute coronary syndromes 2
• Physiologically elevated in pregnancy, trauma, and tissue injury 2