Fibrinogen Unit Converter
Fibrinogen Unit Converter
Convert fibrinogen between g/L, mg/dL and µmol/L, with the replacement thresholds and the reason a Clauss result and a PT-derived result are not interchangeable.
Fibrinogen converter
Mass ⇄ molarFibrinogen 3.1 g/L
Formulae and conversion factors
µmol/L = g/L × 2.94118
g/L = mg/dL ÷ 100
- × 100
- g/L to mg/dL is a unit conversion only — 1 g/L is 100 mg/dL
- 2.94118
- derived from a fibrinogen molecular mass of 340,000 Da: 1 g/L ÷ 340,000 g/mol × 1,000,000 µmol per mol
- 340,000 Da
- the assembled plasma fibrinogen molecule. Molar reporting is rare in practice, so treat µmol/L as a unit conversion rather than a clinically meaningful concentration
Worked example
Fibrinogen 3.1 g/L
3.1 × 100 = 310 mg/dL
3.1 × 2.94118 = 9.12 µmol/L
Within the usual adult range of 2.0 to 4.0 g/L
Fibrinogen thresholds in all three units
| g/L | mg/dL | µmol/L | Significance |
|---|---|---|---|
| 1.0 | 100 | 2.94 | Bleeding risk rises steeply below this; replacement usually considered |
| 1.5 | 150 | 4.41 | Threshold commonly used in obstetric haemorrhage |
| 2.0 | 200 | 5.88 | Lower limit of the usual adult range |
| 3.1 | 310 | 9.12 | Mid-range adult value |
| 4.0 | 400 | 11.76 | Upper limit of the usual adult range |
Reading fibrinogen, and which assay produced it
Grams per litre is the standard reporting unit for fibrinogen, milligrams per decilitre is used in the United States, and the two differ by a factor of one hundred. The molar unit is a different matter. It is derived from a molecular mass of 340,000 Da, and molar reporting of fibrinogen is rare in clinical practice, so µmol/L is best treated as an arithmetic conversion rather than as a meaningful expression of concentration — there is no threshold anyone works to in those units.
Fibrinogen is an acute-phase reactant, and that changes how a normal result should be read. In sepsis, major trauma or established disseminated intravascular coagulation, the level should be rising with the inflammatory response, so a value sitting in the middle of the reference interval may be inappropriately low for the degree of illness and may already reflect consumption. A falling trend across serial samples is more informative than any single number, and a fibrinogen that drops while the C-reactive protein climbs is a meaningful pattern.
The assay matters too. The Clauss method — measuring the clotting time of diluted plasma after a high concentration of thrombin — is the reference method and the one thresholds are based on. A fibrinogen derived from the optical signal of the prothrombin time is a by-product of a different test, requires no extra reagent, and characteristically reads higher, particularly in the situations where the answer matters most, such as DIC and after colloid infusion. The two are not interchangeable, and a laboratory should state which it reports.
Below roughly 1.0 g/L the risk of bleeding rises steeply and replacement with cryoprecipitate or fibrinogen concentrate is usually considered. In obstetric haemorrhage the working threshold is higher, commonly around 2 g/L, because fibrinogen is physiologically raised in late pregnancy and an early fall predicts progression to severe haemorrhage. Sampling technique also affects the result: a difficult draw, an underfilled citrate tube or a very high haematocrit all alter the citrate-to-plasma ratio and shift the measured value.
Frequently asked questions
How do I convert fibrinogen from g/L to mg/dL?
Multiply by 100. A fibrinogen of 3.1 g/L is 310 mg/dL. To go the other way, divide the mg/dL value by 100.
Is the µmol/L figure clinically useful?
Not really. It is derived from a molecular mass of 340,000 Da, but fibrinogen is not reported or acted on in molar units in practice, so treat µmol/L as a unit conversion rather than a concentration anyone works to.
Why can a normal fibrinogen still be a concerning result?
Because fibrinogen is an acute-phase reactant. In sepsis or DIC it should be raised, so a mid-range value may be inappropriately low for the degree of inflammation and may reflect consumption already under way. The trend matters more than the single value.
Are the Clauss and PT-derived fibrinogen results interchangeable?
No. Clauss is the reference method and the basis for published thresholds. The PT-derived result is calculated from the optical signal of the prothrombin time and reads higher, especially in DIC and after colloid, so the method should be stated with the result.
At what level is fibrinogen replaced?
Below roughly 1.0 g/L in general bleeding, where the risk of bleeding rises steeply. In obstetric haemorrhage a higher threshold, commonly around 2 g/L, is used, because the level is physiologically raised in pregnancy and an early fall predicts severe haemorrhage.
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References
- Clauss A. Gerinnungsphysiologische Schnellmethode zur Bestimmung des Fibrinogens. Acta Haematologica. 1957;17:237–246.
- Clinical and Laboratory Standards Institute. Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays and Molecular Hemostasis Assays. CLSI guideline H21.
- Royal College of Obstetricians and Gynaecologists. Prevention and Management of Postpartum Haemorrhage. Green-top Guideline No. 52.