Home › Biomarkers › Fibrinogen
In a large study of 154,211 participants from 31 studies, a higher fibrinogen level was linked to a greater risk of conditions of the heart and the blood vessels in the brain. This applied to healthy middle-aged adults.[1]
On this page you can read what fibrinogen is, what the guidelines say about a value that is too low or too high, what affects your value and which other values are best read alongside it.
Also known as: serum fibrinogen, plasma fibrinogen, factor I. At the lab: FIBR.
Fibrinogen is a protein your liver makes. It helps stop bleeding by helping blood clots form.[2]
A blood test shows how much fibrinogen is in your blood. All it takes is a tube of blood. You don't need to do anything special to prepare.[2]
You may also see this level called serum fibrinogen, plasma fibrinogen or factor I.[2]
A doctor may order this test if your blood does not clot properly, for example if you bleed very heavily.[2]
In a large study, the same held in every age group: the higher the usual fibrinogen level, the greater the risk of conditions of the heart and the blood vessels in the brain. There was no clear threshold above which that risk only began.[1]
The study shows a link, not a cause. Whether a high fibrinogen level itself leads to such a condition needs further research.[1]
The test can also be done if you are pregnant and the placenta comes away from the wall of the womb.[2]
Labplusarts, the lab BioProfile works with, uses a reference range of 2.0 to 4.0 g/l for fibrinogen. The lab calls a level between those limits normal.[3]
| Value | What it can mean | Who it is for |
|---|---|---|
| 2.0 to 4.0 g/l (200 to 400 mg/dL)[2] | Normal range | Anyone who takes the test; the range may differ slightly from lab to lab |
| Outside the normal range[2] | Can point to a shortage, excessive consumption, breakdown of fibrin, heavy blood loss or inflammation | Anyone who takes the test; discuss what it means with your doctor |
| Measured if you are pregnant[2] | The test can be done if the placenta comes away from the wall of the womb | People who are pregnant |
Source: MedlinePlus, U.S. National Library of Medicine. General information about the fibrinogen test, with no separate limits by age or sex.[2]
A low level may point to a fibrinogen deficiency, either present from birth or developed later. It may also point to your body using up too much fibrinogen, to fibrin being broken down, or to heavy blood loss. Your doctor will explain what your result means.[2]
A level outside the range may point to inflammation. In a large study of healthy middle-aged adults, a higher level was linked to a greater risk of conditions of the heart and the blood vessels in the brain. Whether fibrinogen itself is the cause needs further research.[2, 1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Inflammation in your body can push your fibrinogen level outside the range.[2]
If you lose a lot of blood, or your body uses up too much fibrinogen, your level may be outside the range. The same goes if fibrin is broken down faster.[2]
A fibrinogen deficiency can be present from birth, but it can also develop later in life.[2]
If you are pregnant and the placenta comes away from the wall of the womb, a doctor may have your fibrinogen measured.[2]
Fibrinogen is included in BioProfile 150.[4]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
