What Does Fibrinogen Mean on a Blood Test?

What it means

Fibrinogen is one of the clotting factors, the proteins in blood that work together to stop bleeding. It is made in the liver. When a blood vessel is damaged, fibrinogen is changed into fibrin, a sticky mesh that holds platelets together and forms a firm clot.

A fibrinogen level is usually part of a clotting screen. Doctors check it when someone is bleeding heavily, before some surgery, during serious illness, in pregnancy complications, or when other clotting tests are abnormal. A low level can mean fibrinogen is being used up faster than the liver can make it, or that the liver is not making enough. Fibrinogen also rises during inflammation, infection and pregnancy, so a high result is often part of the body's general response to illness.

Fibrinogen and fibrin are easy to confuse. Fibrinogen is the raw material floating in the blood, and fibrin is the finished mesh in a clot. D-dimer is a piece left behind when fibrin is broken down.

Where you may see it

• Coagulation or clotting screen results, printed with PT, INR and APTT
• Blood results during heavy bleeding, for example after childbirth or surgery
• Intensive care blood tests during severe infection
• Liver clinic results, as the liver makes fibrinogen