Fibrinogen test: normal range and results
Equivalent to 200–400 mg/dl in the original source — MedlinePlus
- Updated
- 2026-09-10
- Every number with its source
What fibrinogen is and what it shows
Fibrinogen is a protein made in the liver. It circulates in the blood in an inactive form and is one of the last steps in the blood-clotting chain. When a blood vessel is damaged, the enzyme thrombin converts fibrinogen into fibrin — a mesh of threads that, together with platelets, forms a clot and stops the bleeding. This is why the amount and the activity of fibrinogen directly affect whether the body is able to stop bleeding in time after an injury or an operation.
Fibrinogen is also an acute-phase protein: the liver makes more of it during inflammation or infection, much as it does with C-reactive protein. The test is most often done together with other clotting markers — the prothrombin time (PT/INR) and the activated partial thromboplastin time (aPTT) — when the question is why bleeding will not stop, or why clotting tests are outside their ranges.
Reference range
| Group | Range, g/l | Source |
|---|---|---|
| Adults Equivalent to 200–400 mg/dl in the original source — MedlinePlus | 2.0–4.0 | MedlinePlus Reviewed 2025-02-03 |
This range is for adults. The exact interval a laboratory uses can differ slightly depending on the method — you will find it on your own result sheet.
When the test is done
- When there are problems with blood clotting, for example unusually heavy or unusual bleeding
- When other clotting tests (the prothrombin time, aPTT) are outside their ranges and the cause has to be found
- When disseminated intravascular coagulation (DIC) is suspected — the body uses up clotting factors too fast
- Before major surgery, when it is important to assess the blood's ability to clot
- During pregnancy, if the placenta is suspected to have detached from the wall of the womb
How to prepare
- No special preparation is needed — neither fasting nor any other restriction is required before the test
A raised fibrinogen
A raised fibrinogen most often reflects the body's response to inflammation or infection, because it is an acute-phase protein whose production in the liver speeds up at those times. When the result is assessed, the whole clinical context matters — whether there was an infectious or inflammatory illness at the time. A doctor explains the meaning more precisely, together with other tests such as CRP.
- Inflammation in the body
- Infection
What to discuss with a doctor: whether there was an acute infection or inflammation at the time of the test; the other inflammation markers, for example CRP, assessed together with fibrinogen; and when it is worth repeating the test so that the change over time can be seen.
A low fibrinogen
A low fibrinogen means the body has less of it than normal clotting requires — most often because too much is being used up, because of a congenital or acquired deficiency, because fibrin is breaking down, or because of a large loss of blood. Such a state can increase the risk of bleeding and is usually tested together with other clotting markers.
- Too much fibrinogen being used up in the body, for example in disseminated intravascular coagulation (DIC)
- A congenital fibrinogen deficiency, or one acquired after birth
- Breakdown of fibrin (fibrinolysis)
- A large loss of blood (bleeding)
What to discuss with a doctor: the other clotting tests — the prothrombin time (PT/INR) and aPTT — to narrow down the cause; whether there are signs of active bleeding; an assessment of liver function, since the liver makes fibrinogen; and when it is worth repeating the test so that the change over time can be seen.
Related indicators
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Frequently asked questions
›What is the normal fibrinogen level in blood?
According to MedlinePlus, the normal fibrinogen level in adults is 2.0–4.0 g/l (equivalent to 200–400 mg/dl). The exact laboratory interval can differ slightly depending on the method used — you will find it on your own result sheet.
›Why does a doctor order a fibrinogen test?
The test is most often ordered when questions arise about blood clotting — for example when bleeding is unusually heavy, or when other clotting tests (the prothrombin time, aPTT) are outside their ranges and the cause has to be found.
›What does a low fibrinogen mean?
A low fibrinogen means the body has less of it than normal clotting requires. The causes are too much being used up (for example in DIC), a congenital or acquired deficiency, the breakdown of fibrin, or a large loss of blood. The exact cause has to be discussed with a doctor.
›Does a raised fibrinogen always mean there is a problem?
Not always. Fibrinogen is an acute-phase protein, so its level rises naturally during an infectious or inflammatory illness. Other tests, such as CRP, and the overall clinical picture help to explain the result more precisely.
›Do I need any special preparation before a fibrinogen test?
No. According to MedlinePlus, this test needs no special preparation such as fasting.
›Which other tests is fibrinogen usually assessed with?
Fibrinogen is most often assessed together with the prothrombin time (PT/INR) and the activated partial thromboplastin time (aPTT) — together these tests help to establish where in the clotting chain the problem lies.
Sources
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.