Fibrinogen

Some laboratories use 2.0 to 4.0 or 1.8 to 3.6 g/L; it rises in pregnancy and with age; use the range your lab printed.

Fibrinogen is a protein made by the liver that is converted into fibrin, the mesh that holds a blood clot together. It is also an acute phase protein, so it rises whenever there is inflammation. The test measures how much is in the plasma.

Doctors request it as part of a clotting screen when someone is bleeding or bruising, in severe illness where clotting factors may be used up, in liver disease, before some operations, and occasionally as a marker of inflammation.

• Inflammation or infection from any cause
• Pregnancy and oestrogen-containing medicines
• Smoking
• Older age
• Obesity and diabetes
• Some cancers
• Recent surgery or injury

• Severe liver disease
• A severe illness that uses up clotting factors (disseminated intravascular coagulation)
• Massive bleeding or transfusion
• Some medicines, including some used to dissolve clots, asparaginase and some anticonvulsants
• Rare inherited shortages

• Any recent cold, infection or inflammation raises it
• It rises through pregnancy as an expected change
• Smokers sit higher in the general population
• Some direct oral anticoagulant medicines interfere with some laboratory methods

No fasting needed. Citrate tube. A value taken during an infection is best repeated when well.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.