Fibrinogen optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for Fibrinogen:
- Optimal 200 – 300 mg/dL (2 – 3 g/L); sufficient 150 – 400 mg/dL (1.5 – 4 g/L); out of range below 150 or above 400 mg/dL.
Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| mg/dL | 200 – 300 | 150 – 400 | below 150 or above 400 |
| g/L | 2 – 3 | 1.5 – 4 | below 1.5 or above 4 |
What the evidence says
The acceptable band of 150 to 400 mg/dL (1.5 to 4.0 g/L) is a laboratory reference range. Laboratories differ: several start at 200 mg/dL (2.0 g/L), and Labcorp's adult range runs to 464, so read the result against the reporting laboratory's own range. The optimal band of 200 to 300 mg/dL (2 to 3 g/L) is a functional target, and the evidence does not sit neatly inside it: in an Italian cohort of 17,689 adults the lowest-risk group sat at about 3.0 to 3.2 g/L, and women below 2.6 g/L had higher mortality. A clotting factor and an acute-phase reactant at once, so the same raised value means different things depending on why it was ordered. Higher in pregnancy, on the combined pill, in smokers and with age; low in advanced liver disease and in consumptive coagulopathy. Read beside hsCRP.
Sources
- Fibrinogen – Clauss — Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle Laboratories test directory, 2026 · Laboratory / reference-interval sourceAdult reference range for Clauss fibrinogen of 1.5 to 4.0 g/L, the same as Sera's sufficient band. Page last updated 28 January 2026.
- Fibrinogen blood test — MedlinePlus Medical Encyclopedia, US National Library of Medicine, 2025 · Government / public-health guidanceNormal range of 200 to 400 mg/dL (2.0 to 4.0 g/L). Matches Sera's sufficient upper edge; its lower edge is 200, not Sera's 150. Reviewed 3 February 2025.
- Clauss Fibrinogen — North Bristol NHS Trust, Severn Pathology, 2023 · Laboratory / reference-interval sourceReference range of 2.0 to 4.0 g/L, in force from 24 April 2023. Matches the upper edge and shows that UK laboratories differ on the lower one (1.5 or 2.0).
- Fibrinogen Activity (test 001610) — Labcorp test directory, 2026 · Laboratory / reference-interval sourceReference interval for people over 16 of 209 to 464 mg/dL, from Labcorp's own study. Wider at the top than Sera's 400: a result of 401 to 464 is in range at Labcorp. Current directory entry, opened October 2026.
- Plasma fibrinogen levels and all-cause and cause-specific mortality in an Italian adult population: results from the Moli-sani study — Parisi R, Costanzo S, de Laat-Kremers R, Di Castelnuovo A, et al. — Bleeding, Thrombosis and Vascular Biology, 2023 · Peer-reviewed publicationIn 17,689 Italian adults followed 11.2 years, women in the lowest fifth (1.12 to 2.64 g/L) and the highest fifth (3.62 g/L or more) had higher all-cause mortality than the middle fifth (2.97 to 3.23 g/L); in men risk rose linearly. Does not support an optimal band of 2 to 3 g/L. Abstract read through the DOAJ record, not Europe PMC.
What Fibrinogen measures
The clotting protein the liver makes, which doubles as one of the acute-phase reactants.
Two things at once: a clotting factor and an inflammatory marker, so a raised value is read differently depending on why it was ordered. It rises in pregnancy, with the oral contraceptive pill, with smoking and with age, and falls in advanced liver disease and consumptive coagulopathy. Read it beside hsCRP rather than alone.