Blood
Fibrinogen
Also known as: Factor I
CONVERT & COMPARE
mg/dL
=
3.5
g/L
Reference ranges by source
Published adult intervals: 4, from 4 named sources, shown in mg/dL.
SOURCE
SEX
AGE
RANGE
VISUAL
CITE
About Fibrinogen
Coagulation factors are proteins in your blood. They help form blood clots to stop bleeding when you have an injury. Fibrinogen, also called factor I, is one of these clotting proteins, and it plays an essential role in forming a blood clot.
Coagulation factor tests are blood tests that check one or more of your clotting factors to see if you have too much or too little of a clotting factor, are missing a clotting factor, or have a clotting factor that isn't working right.
Your liver makes most of your clotting factors, including fibrinogen. Fibrinogen is also an 'acute-phase' protein, which means its level naturally goes up during inflammation, infection, pregnancy, or after an injury or surgery.
Main source: MedlinePlus ↗
Useful for
Finding out if you have a problem with any of your clotting factors that may cause too little or too much blood clotting
Checking on people who have a known problem with clotting factors
Helping evaluate bleeding disorders, since low fibrinogen can lead to bleeding problems
Checking on people who take blood thinners to lower the risk of blood clots
Main source: MedlinePlus ↗
Interpretation
Lower than normal fibrinogen can lead to bleeding problems. It can be caused by rare inherited conditions, severe liver disease, malnutrition, or a serious clotting problem in which the body uses up clotting proteins faster than it can make them (called disseminated intravascular coagulation or DIC).
Higher than normal fibrinogen is often a sign of inflammation, infection, recent surgery, pregnancy, or estrogen use rather than a true clotting disorder. Levels that stay high over time have been linked to a higher long-term risk of blood clots in arteries and veins.
Because fibrinogen rises with inflammation, your provider will usually look at your result alongside other tests and your symptoms, not on its own.
For general wellness information only. Talk to a clinician about your specific results.
Main source: MedlinePlus ↗
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Related biomarkers
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Sources
Last updated 2026-05-02
This page presents source-specific reference data and sourced explanations. For general wellness information only. This is not medical advice. For diagnosis or treatment of any condition, talk to a qualified clinician.