What is the normal fibrinogen level?

Normal Fibrinogen Levels

The normal plasma fibrinogen level ranges from 2.0 to 4.5 g/L (200-450 mg/dL). 1

Understanding Fibrinogen

Fibrinogen is a critical coagulation protein that serves as the precursor to fibrin, the primary structural component of blood clots. It plays an essential role in hemostasis and is one of the first coagulation factors to reach critically low levels during major bleeding events.

Clinical Significance of Fibrinogen Levels

• Low fibrinogen levels (<100 mg/dL) are associated with spontaneous and procedure-related bleeding, particularly in patients with cirrhosis 2
• Moderate levels (100-150 mg/dL) may still present increased bleeding risk, as recent clinical data suggest that fibrinogen levels <150-200 mg/dL are associated with increased peri- and postoperative bleeding 3
• Target levels during active bleeding should be maintained above:
  • ≥100 mg/dL (1.0 g/L) for general bleeding scenarios 1
  • ≥150 mg/dL (1.5 g/L) for patients with DIC and active bleeding 1
  • 150-200 mg/dL for severe hemorrhage 1

Fibrinogen in Special Clinical Scenarios

Pregnancy and Delivery

• For women with congenital fibrinogen disorders during pregnancy, a trough fibrinogen level of ≥1 g/L (100 mg/dL) should be maintained throughout pregnancy 2
• For labor, delivery, and neuraxial anesthesia, higher levels of ≥1.5 g/L (150 mg/dL) are recommended 2

Liver Disease

• In patients with cirrhosis, fibrinogen levels <100 mg/dL are associated with bleeding complications 2
• A fibrinogen threshold from 100 to 200 mg/dL has been recommended for fibrinogen replacement in the setting of bleeding in cirrhosis, with 120 mg/dL being the most commonly used cut-off 2

Trauma and Surgery

• In trauma patients, fibrinogen reaches critical values earlier than other procoagulatory factors 3
• While a threshold of 100 mg/dL has traditionally been recommended, recent evidence suggests maintaining levels between 150-200 mg/dL to prevent excessive bleeding 3

Measurement Methods

• Clauss method is preferred for clinical assessment of functional fibrinogen levels 1, 4
• PT-derived methods may overestimate fibrinogen levels in patients with dysfibrinogenemia (by approximately five times compared to the Clauss assay) 4
• Viscoelastic testing (ROTEM/TEG) can provide functional assessment of fibrinogen in addition to plasma levels 1

Common Pitfalls in Fibrinogen Assessment

1. Overreliance on PT-derived methods - These can significantly overestimate functional fibrinogen levels in patients with dysfibrinogenemia, potentially leading to undertreatment 4

2. Using a single threshold for all clinical scenarios - Different clinical situations require different target fibrinogen levels (e.g., higher levels for severe hemorrhage vs. maintenance)

3. Delayed assessment - Fibrinogen is often the first coagulation factor to reach critically low levels in massive bleeding, requiring early and frequent monitoring 1

4. Ignoring fibrinogen in DIC - While low fibrinogen is classically associated with DIC, 47% of DIC patients may have fibrinogen levels >200 mg/dL, making it an insensitive marker for DIC diagnosis 5

Understanding normal fibrinogen levels and their clinical implications is essential for proper diagnosis and management of bleeding disorders, particularly in critical care settings where timely intervention can significantly impact patient outcomes.